I have what might be a dumb question: what makes something a gaming keyboard? Is there something that makes it specifically better for gaming? Cool RGB lighting? Simply aesthetic choices?

I don't know, but I can can give you some guesses as to what I'd call at least theoretically legitimate features (though the actual features might be aesthetic):

• Some keyswitches have linear force; these are apparently considered to be preferable for games. Low resistance for quicker response. Cherry MX Red switches are often billed as for gaming and have these properties.

• N-key rollover is pretty common (a controller capable of detecting any arbitrary key being down on the keyboard, up to N keys) but it's a legit feature for some games that do rely on hitting a lot of keys simultaneously. I recall using a keyboard with a more-limited grid encoder, playing the original Team Fortress, and occasionally legitimately hitting the limits on what the keyboard encoder could detect; it was annoying when it happened.

• Probably not what they're selling, but USB imposes protocol limitations on how many keys can be down at once. Basically, USB sends the whole state of the keyboard. PS/2 does not -- it is edge-triggered, just tells the keyboard when a key goes down. If an event gets missed, that means that PS/2 can have a key appear to be "stuck" down until it's tapped again. However, USB can only send so many keys in the key state, which bounds how many keys can actually be down (though IMHO it's at a limit that is so high that it doesn't matter), whereas PS/2 can send an unlimited number of keys down. I know that PS/2 used to sometimes be sold specifically for this characteristic.

• Possibly macros, though I'd think that it'd be possible to better do that in software on the host machine. Putting it on the keyboard might be a way to defeat anti-cheating systems, I suppose.

• T-shape arrow keys or possibly a numpad are necessary for some games. Ditto for F-keys. Not all laptops will have these (well, they probably have the F-Keys, but you might have to chord with Fn or something). Some games make use of arrow keys, a lot of older games used to use the numpad, and some relatively-new games make use of F-keys (by convention on Windows, F5 and F9) for quicksaves and quickloads.

• Maybe lighting that integrates with games.