The origin of frame data (as the name implies) is from taking a frame by frame analysis of moves in a fighting game. So, for a lot of current games like SF4, the game runs at 60 Frames per second. You take a move, such as a jab, and count the frames it takes to start up, how many it takes to hit, and how many it takes to recover. Then you see how it affects the opponent - when does it hit? how long are they hit for? When you compare these to another character, it defines how your character will "play" in the game.
For the sake of analysis, I'll be describing frame data using Street Fighter 4 (mostly because of its popularity and availibility).
Let's Start with the terminology that will be used to describe frame data.
Each move has a set of fields that describe its properties, and they go as follows.
Startup: The startup of a move is how fast a certain attack comes out before it can hit an opponent. Startup data also describes what can link from one move to another.
Active: Active frames describes how long a move actually hits for, and is a big part of how "meaty" attacks work.
Recover: Recovery frames are how long after hitting the opponnent (i.e. startup+active) that the move recovers for you to go back to neutral or to have another move come out.
Total: The total frames are the full count of frames that a move has, from start to finish.
Frame Advantage Block: This describes how long a person is in blockstun after they are hit with your move. If it is +, then you recover before they do, and if it is - then they recover first.
Frame Advantage Hit: Same as above, except for on hit. This sometimes is part of the calculation to tell if something can combo or link, as the opponent is in hit stun for these frames.
Blockstun: During this amount of frames, the opponent cannot get out of the block animation. (On block by opponent)
Hitstun: During this amount of frames, the opponent cannot get out of the hit animation. (On hit by opponent)
Damage: This is the amount of damage a move has. If it has multiple hits, an asterik is used. If the attack has early and late damage, you see parenthesis.
Stun: This describes the amount of stun a move makes to get a character to the dizzy state. Usually Medium or heavy moves do more stun, but there are some special moves that will induce more stun than damage as well.
Meter Gain: In SF4, your super meter will gain if you do special moves. This field shows the amount gained on hit or block of the move. Usually this is described by Hit/Block int the field.
Block: Describes if it can be blocked High or Low, i.e. stand block or crouch block. If it can be blocked by both, it is labeled "HL"
Cancel Ability: Shows moves that can be canceled out of their recovery frames. Moves will say either C,Sp, or Su (referencing eventhubs frame data).
C stands for Chain, Sp is Special, Su is Super. More on this later.
Now that we've gone over the basic terminology, lets go over some of the special cases and some basic calculations of how frame data works.