How to request move take back.

Hello there, I am still new on this site and I was surprised when in one of my games, the opponent requested to take back his move. My question is how do you do that? Is there a button to click to request your opponent to allow you to take back the last move you made? By the way I allowed him since it was just a casual game. Thanks in advance for your reply.

While playing a game, to the right of the board, in between the players' user names, there are often three buttons. The arrow is the takeback request, the hand is a draw offer, and the flag is to resign. There is an option to not allow takebacks, so the arrow will be absent if this option is selected.

Have fun!