Frame data explains the start up, block advantage, and recovery of moves you do.
Lets take a look at a move like flashes lightning uppercut.
Note: im taking these numbers from the wiki, if they are incorrect, blame the wiki. The explanations of what they mean are whats important.
Startup: 6 frames. This means that it takes 6 frames (6/60ths or 1/10th of a second) for the move to go active after you input it. All moves are measured in this type of data format (number of frames).
Hit advantage: 58 frames. This means that if you hit your opponent with this move, there is a 58 frame window (essentially 1 second) where you can move around on the screen, and your opponent can't. For this specific move, it is because you have knocked them down. So you can move for a second while they are on their back to reposition yourself.
Block advantage: -17. This means that if your opponent blocks this move, there is a 17 frame window where they can move, and you can't.
What do these three things mean to you?
Frame data tells you whether a move is "safe" or "punishable"
Safe means if you do a move, and immediately hold block, no matter what your opponent does, you can defend against their attack.
Punishable is the opposite. If you do a move and immediately hold block, you still can get hit by their follow up attack.
Lets go back to lightning uppercut. Since its block advantage is -17, if your opponent does any move with less startup than that gap, you will not be able to block, and therefore "punished".
Further, frame data tells you what move will hit first if two moves are input at the same time. If you input flashes lightning uppercut (6 frame startup) at the same time your opponent does a move with a 10 frame startup, you will hit first because your move is active 4 frames faster.
Those are the basics, hope it helps!
