I don't understand. The human or computer could make different moves...? Thus making this pointless?
The computer and the human you are playing against are free to make moves. Now you see the human, when he makes his move, you use that move on the computer, the computer's response is yours on to the human. Basically you are copying the humans moves as your own so when the computer responds to it, you will know how to yourself. Example:
Human MatchYour opponent makes first move.
Computer MatchYou make the first move your human opponent did, thus emulating what the he did onto the computer. The computer soon responds with a move of his own.
Human MatchTake the move the computer made and make it onto your human opponent. He responds to it. Rinse and repeat.
Seems like Guana beat me to it, but yeah that is how it all works. I would never do it, though. I have a little more honor than that.