Guilty Gear's Buttons: Here's the Rundown

Guilty Gear is one of those rare fighting games that uses 5 buttons by default. Naturally, this often leads to newcomers being thoroughly confused as to how they should configure their buttons or have difficulty grasping the traditional default layout. To help you work this all out, let's have a talk about what each button actually does in the game. If you're feeling uncomfortable when playing, hopefully this will ease some of that.

Punch (P)

Punches are the jabs of Guilty Gear. They're almost always the fastest normals a character has. With the exception of Axl's crouching Punch, they can chain into themselves. In other words, you can mash those punches all day. Are you blocking someone and reckon they're going to try something trick instead of a frametrap? Mash that jab. See someone stuff up oki as they approach you and want more reward than throwing? Mash that jab.

Standing Punches (5P) are commonly a fast move that can be used as an antiair in a pinch. While they're not going to be trading in your favour, they can be handy to try catching people jumping away from you without committing to a string that'll let them get away once it ends.
Compare 5P to other games': 5A (Blazblue, Melty Blood). Stand jabs (Street Fighter). Magneto and Nova's jabs (Ultimate Marvel vs Capcom 3).

Crouching Punches (2P) are extremely fast and usually advantageous on block. You're not going to be hitting low with these guys, but tapping it a couple of times, making a step forwards then doing so again can keep people honest and wear at their patience. They'll chain to just about everything in your toolset, making them a great way to start off whatever method you feel like for opening people up. If your character has no other dedicated frametraps, they probably have a good 2P.
Compare 2P to other games': Crouch jabs (Street Fighter), 2A (Blazblue, Melty Blood)

Holding forwards and pushing Punch (6P) provides you with a button that usually leans forwards and upwards. With the exception of Elphelt, the upper body of your character is invincible and will simply ignore anything thrown at it. The obvious use is to catch people airdashing at you while pushing a button. Depending on you character's height, this can also catch things like, say, Far Slashes. Do note that this is strike invulnerability. Projectiles will still hit you.
6Ps also have a lot more recovery on whiff than 5Ps. Thus, while better at keeping your antiair from trading with someone approach you, be mindful that they can be baited with double jumps or airdashing away. The answer to a double jump is to airthrow them.
Compare 6P to other games': 6A (Blazblue), Rising j.A (Melty Blood), Antiairing with stuff like Chun-li st.HP (Street Fighter)

Kick (K)

It's easy to picture the Kick button as being the Light Kick to accompany the Punch button being mostly Light Punches. However,  it's a bit more complicated than that. Unless your Chipp, the K button has more in common with things like Medium Kick in Street Fighter than, say, the mashable crouching light kicks of a 4 button game like The King of Fighters. This and the Slash button tend to trip people up, so it's important to get that they do.

Standing Kicks (5K) tend to come in one of three varieties:

 - Standing Lows. (e.g. Ky, Zato, Elphelt, Potemkin) These will usually be some sort of kick to the shins. They'll chain into most heavier buttons and serve as a quick low to catch someone who thinks you're going for a Dust or pressuring with an airdash in. Use the advantage from a 2P then wait a bit before hitting 5K. You'll be surprised how often this can catch people!

 - Antiair Kicks. (e.g. Sol, Faust, Ramlethal) These are usually fast or have some ridiculous counterhit property that let you capitalise even in the event of a trade. Sol's 5K is a 3 frame normal, making it one of the fastest moves in the game. Faust's 5K cases wallbounce on counterhit, resulting in him getting that darn Faust Combo even when it trades.

 - Footsie Button. (e.g. Slayer, Axl, May) Some characters' 5K are simply another button to play footsies with. In Axl's case it's because his Punch buttons are tied to long limbs. In Slayer's it's because his Slash buttons are all close-combat attacks. In XX, May's 5K is immune to throws. Sadly that's not the case in Xrd.

Compare 5Ks to other games': Lows - st.LK (Street Fighter), Kohaku 4B (Melty Blood), Yuzuriha and Gordeau 5A (UNIEL)

Antiairs - Various st.MK and st.HK (Street Fighter) Bullet 6B (Blazblue), Raw S xx Fly (UMVC3)
Footsies - Ryu st.MK (Street Fighter), 5B (Blazblue, Melty Blood), st.B (KOF)

Crouching Kicks (2K) are your go-to fast, far reaching low. Unlike KOF, these aren't mashable (unless you're Chipp or Milia) so you'll want to stagger these at range to safely catch people pushing buttons, or chain into something with more advantage or that's jump cancellable in order to continue your offense.
Compare 2Ks to other games': cr.LK, cr.MK (Street Fighter), Sion 2A (Melty Blood, UNIEL), 2B (Blazblue), cr.HK (Yatagarasu)

Since Kick buttons are fast, have good reach and are one of the most common ways to land a hit on offense, a great deal of them have negative proration. This means that regardless of how many hits the combo goes for, it will be doing less damage from the get-go when compared to something like a Close Slash or Standing Heavy.

Towards+Kick (6K) is a button that some characters have. There's pretty much two main types of these:
 - Pressure or Combo Extension. (e.g. Ky, Jam, AC+R Testament, Baiken, Order-Sol) These tend to be slower than your 5K or 2K, but have more advantage on block. A reward for leaving a gap in your string. In XX, Baiken and Order-Sol's are throw-invulnerable to boot!
 - Another Standing Overhead. (e.g. Xrd May, Slayer, Milia, Zato). An extra overhead to help mix up what you do on offense! How much advantage or whether they're special cancellable is entirely dependent on the character.
There's a few other weird ones such as Axl's 6K (which is another angled anti-air attack), but their use should be fairly obvious by just looking at the thing.
Compare 6K to other games': Pressure/Combos: Ryu's fwd+HP (Street Fighter), Most command normals (KOF),  Kohaku's 4B (Melty Blood)
Overheads: Ryu's fwd+MP (Street Fighter), Kim's fwd+B (KOF), Universal Overheads (Street Fighter 3), Ragna 6B (Blazblue), Sion's 6B (Melty Blood, UNIEL)

Slash (S)

Slashes are a curious melting pot of what would fill the Medium Punch and Medium Kick buttons on Street Fighter, or the Heavy buttons in a 4 button game like KOF. You're not going to see many highs or lows from these guys, but their lack of damage proration and large hitstun (particularly on counterhit) makes them great for starting the seriously damage punish combos. They also have something unique going on if you're standing and hit that S.

There are two types of Standing Slash (5S) depending on your distance from the opponent: Close Slash (cl.S) and Far Slash (f.S). cl.S chains into f.S if you tap the S button twice. This means you can still access the f.S if you're up close, and leads to the curious Slayer combo where f.S links back into cl.S. Thus, (cl.S, f.S)x2 is a command part of Slayer's pressure and combos up close.

Clash Slash (cl.S) buttons commonly do solid damage, hit mid and have a strong vertical hitbox. They'll catch people jumping away, and are a good button to use if you're punishing someone coming down from the air. Such as, say, after you blocked Sol's Volcanic Viper or want to tag someone who whiffed a Jumping Heavy on the way down. Their greater amount of blockstun means that if you jump cancel one, you're not going to get caught by someone mashing on your way up.

Compare cl.S to other games': cl.MP (Street Fighter), Iori and Kyo's cl.C (KOF), Arcueid's 5B (Melty Blood), Gordeau's 5B (UNIEL)

Far Slash (f.S) buttons are almost always the longest ranged normal in your arsenal. Don't expect to net a full combo off of these at maximum range without a counterhit or spending some meter (which Xrd's timeslow makes much easier than it was in XX). Numerous characters' Crouching Slash recovery quickly on whiff, allowing them to reduce the recovery from a f.S being blocked and continue their approach. Use these to assert your position and stop people trying to other run away from you or stuff whatever move they were trying for next. You want to get rid of that pesky Eddie crawling up to you? f.S. Want to do a meaty on someone's wakeup and are concerned they'll be mashing something? f.S. Want to make people miserable? Be Faust and cancel f.S into item toss.

Compare f.S to other games': st.MK (Street Fighter), 5B (Blazblue, Melty Blood), f.D (KOF)

Crouching Slash (2S) buttons have far less reach than f.S, but often more than 2S. If you're going to have a heavier hitting low than a kick, it's probably assigned to this button. As mentioned above, see how quickly it recovers on whiff. If it's good, chain f.S to 2S at range to maintain your approach. If it's a low, establish that you only go for lows with Kicks, then do something unexpected like a 5P into 2S and see what happens to your opponent. If you're hitconfirming with punches, chaining to 2S is going to lead to some more damage than moving from P to K would.

Compare 2S to other games': cr.MP (Street Fighter), 2B (Blazblue, Melty Blood), cr.HK (Yatagarasu)

Heavy Slash (H) [some people use HS, so be wary of that in notation]

Curiously enough, the Heavy Slash line of normals are heavy hitters. These are what you want to tack into combos for extra damage, and if possible start a combo with one when punishing something dumb. 

Standing Heavy (5H) is usually a damaging attack with horizontal reach. If anything's going to cause a stagger state on counterhit, it's going to be 5H. Note that I didn't say they're slow. Sometimes these can be faster than Slash attacks (such as Milia's 5H with a paltry 6 frames of startup). However, they are more likely to have longer recovery than Slash attacks, and on block have way less moves to cancel into. They're harder to establish you've hit someone with in a pinch, but you get bigger damage as your reward when you do notice.

Compare 5H to other games': 5C (Blazblue, Melty Blood), f.C (KOF), st.HP (Street Fighter)

Crouching Heavy (2H) is usually the slow yet damaging antiair attack. Don't expect upper-body invulnerability on these. You're using this because someone's jumping at you really obviously and you want to make them suffer for it. On counterhit, expect loads more hitstun or a launch on a grounded opponent. If tagging with a jab, see if you can get something from chaining to 2H afterwards for extra damage.

Compare 2H to other games': 2C (Blazblue), 2B (Persona 4 Arena), cr.HP (Street Fighter), cr.C (KOF), Aoko 3C (Melty Blood), Gordeau's 2C (UNIEL)

Towards+Heavy (6H) is a big, slow, hard-hitting horizontal attack that's almost always going to increase the damage on every hit in your combo should it hit. The exact uses for this move vary from character to character (Ky's is a whopping huge +15 on block, Faust's is an overhead that leads to huge damage from his basic combo,  Sol's is a combo ender to setup a safe-jump), but the basic idea is that since you input Throw by pushing 6H, if someone tries to backdash away from it they will instead get hit by this whopping huge normal into big damage. Since this would also mean that if your throw attempt on defense is baited, either a 5H or 6H is coming out, we have that Option Select I brought up in a previous post. If you want to throw someone and don't care about trying to throw them back into a corner, input 6K+H. If you have a slow 6K, input 6S+H instead. If you want to throw on offense and stop them jumping away, input 6P+H.

Compare 6H to other games':  Level 3 Focus Attack into Ultra (Street Fighter 4), Fatal Counter starters (Blazblue, Persona 4 Arena), Galactica Phantom (KOF)

Dust (D)

The Dust is a pretty simple pair of functions to explain.

Standing Dust (5D) is always an overhead. They're big, somewhat slower than 6K overheads or other options a character might have, but they lead to unique combos. On block, they're either very slightly disadvantageous (and therefore safe at the distance you'd usually use one) or slightly advantageous, rewarding you for getting one out without being smacked around for your efforts. In XX I would explain blocking overheads in Guilty Gear with the rule "if it's slow and looks nothing like an overhead, it's probably a Dust." In Xrd, the game put a big red glow on Dusts to remind you that yes, it's an overhead. Unlike Persona 4 Arena or Dengeki Bunko Fighting Climax, the way to stop a Dust is to see one's coming out and hit a button. If you're quick, something like a 2S will work great. This is why you won't want to be too close when performing one - they can just idly tap Punch instead of paying more attention to what you're actually doing. Don't expect these to open up your opponent every time. Use them in moderation or YRC then do a low or throw to keep people on their toes.

Compare to other games': Universal Overhead (Street Fighter 3 [Zato's works the same way]), All-out Attack (Persona 4 Arena. These have no autoguard though.), 4A+B (Dengeki Bunko Fighting Climax. These have no superarmour though).

Crouching Dust (2D) is always a sweep. A nice, big low that knocks down. Don't know fancy combos and hit someone on the ground? Just chain through to sweep then bait them into doing something dumb as they get up. A lot of these are jump cancellable on block, allowing you to continue pressure if you chain all the way through. Some characters such as Venom, Sol and Anji have 2D animations so low to the ground that they can go under all sorts of things. This is known as a low profile.

 Compare to other games': 3C (Blazblue), 2A+B (Persona 4 Arena. Most are special cancellable). Sweeps (Every 2D Fighting Game Ever), Makoto's cr.MK (Street Fighter 3 and 4, particularly 4. Sol can antiair with 2D the same way Makoto can.)

Jumping Normals

These work much the same way as their grounded counterparts:

j.P is fast, mashable, and has small reach. Use these during an airdash to catch someone still working out what their air-to-air plan wil be.

j.K has good horizontal reach, and is the most likely normal to crossup an opponent.
j.S has a mix of horizontal and vertical reach, and combined with its ability to chain into j.H and j.D is good for starting a jump-in.

j.H have large hitboxes and good blockstun, but if you perform them too early into a jump-in the blockstun will have run out and you'll likely get thrown for your efforts. Space these carefully. They're also almost always one of your few aerial moves that cannot be jump cancelled.

j.D will usually be the heaviest hitting button, with some other property on hit or the ability to be jump cancelled. Do note that these have recovery on landing, making them a risky option for jumping in with.

The most notable curiosity with aerial normals is that most characters' j.K and j.S can be chained backwards into j.P. This often leads to aerial strings such as j.S j.P j.S j.P j.K and so on. Useful in pressure, useful as air combo filler.

So with all that in mind, let's take a look at the default button layouts for Guilty Gear Xrd.

 

Type-A is the series' historical default. B and C are a nod to Blazblue's layout. D and E are derived more from Persona. Do you have a better idea of why buttons are where they are now that you see  the uses they have?

Finally, be aware that you do not have to use a default layout. This is 2015. Unless you're specifically looking to play the game in a Japanese arcade, defaults do not matter. Use whatever you find most comfortable and that makes the most sense to input.