Think of frames as a measure of time. If a player blocks a move of yours that is plus3 on block. You can attack 3 frames before he comes out of block animation and is able to attack you. If your move is minus3 that means that players can come out of block and attack you back 3 frames before you come out of your attack animation and block or continue to attack. If you are neutral then nether one of you have frame advantage. I'm not really into frame data. I'm not that good but thats what I have been taught.
