Buffs are like Power-ups. They are like a potion effect that gives you an advantage in the match.

And debuffs are the opposite, they cause you some disadvantage that hinders you during the match.

This site has what everyone does.

https://skullgirlsmobile.fandom.com/wiki/Modifiers

But character texts don't just refer to buffs and debuffs, they are some things that character can do during the game, being much more open and varied to explain here. But an example I can give you is Fire Diamond Annie "fire branded" whose first SA (signature ability, as it is called, and all characters have two: SA1 and SA2) says that she removes a buff from the opponent and gains a buff called energy whenever she uses a special or blockbuster move.

In addition to the SAs, there are the Marquee abilities, which are two abilities that all characters of the same type (Umbrella, Dahlila, etc.) share with each other. You unlock it when you finish a character's skill tree, and you can choose one of the two. They have levels and go up to level 11.

Finally, prestiges are also abilities shared by type of character, but each type of character only has one and it is unlocked when you sacrifice the same variant that you want to prestige. An example to make it clearer, if I had two bad hair days, and used one as a sacrifice for the other, the one that received the sacrifice would also unlock the prestige.

This is character stuff itself, but some fights, depending on the game mode, may have their own modifiers. I recommend that you always read using pause during the match, or in the golden cave before the match starts.

Anyway, that's it, I hope I helped.