You can set up conditional moves that give your response to anticipated moves by an opponent. The conditional move button appears after you click on submit move if you have your settings set to "stay on this game" or you have no other ready games.
Players use this option to speed up the games when there is a series of forced or obvious moves or if you have a plan you don't want to forget about.
If the other player moves in accordance with the conditional moves you established, your response is played immediately and the other player is informed something like "your moved triggered a conditional move, its your turn again."
As the title says, how is that possible? I'm not talking about the opening.
The match was at 48th move, i played a move, and instead to move me to the next ready on-line game, my opponent respond to my move and he is offline!!
Happened twice from move 48 to 50. How is that possible?