Frame data is the numerical breakdown of a move in a fighting game, measured in frames, covering startup, active frames, recovery, and advantage on hit or block. Fighting games commonly run at 60 frames per second.
A frame is one sixtieth of a second in a 60 frames per second game, the smallest useful unit of fighting game time. Every attack divides into three phases. Startup is the wind up before the move can connect. Active frames are the window when it can actually hit. Recovery is the vulnerable tail before the character can act again. A jab with three frames of startup is fast precisely because the opponent has almost no time to react.
Frame advantage turns those numbers into decisions. If your blocked attack leaves you at plus two, you can act two frames before the defender, so your pressure continues. If it leaves you at minus seven and the opponent has a seven frame punish, that attack is unsafe and a good opponent will take the free damage. Players memorise these values for their own character and for common matchups.
Studied properly, frame data removes mystery from a loss. Instead of feeling cheated, a player can point to the exact exchange: their move was slower, started later, or recovered into a punish window they should have known about.
In play"Check the frame data before you throw that move out, because it is minus on block."