We've known for a while now (since E3, actually) that Halo 4 would offer a wide variety of control schemes for players to choose from. Each control scheme allows you, the player, to pick how you'd like to play the game with a variety of differences in the buttons you'd press to beat someone in melee or throw a grenade, just to cite a couple of examples.
Until now, we've only known of their existence but with very scant details about what each control scheme would actually entail.
The release, or rather, leak of the button layouts shows exactly what's in store with Halo 4. With each of these layouts, you'll be able to play the game precisely how you want to without having to rely upon the developers' intentions of how the game "ought to be played."
In addition to the button layouts, you'll be able to swap the stick layout, look inversion, sensitivity, and more. If you're more keen to snipe your enemies instead of engaging with them in close quarters, it might be a good idea to turn down the look sensitivity to score those headshots.
Boxer
Melee and Throw Grenade are swapped. Sprint and Crouch are also swapped.
Bumper Jumper
Jump and Melee are on the Left and Right Bumpers.
Default
This is the recommended default button layout.
Fishstick
Zoom is moved to the Left Trigger.
Green Thumb
Melee is on the Right Stick click. Zoom moves to the Right Bumper.
Recon
Reload is moved to the Right Bumper.
Southpaw
Left and Right Triggers and Bumpers are flipped.