In chess opponents regularly agree on a timing for the game. If one player has used all the time he may the other wins by time-out.
Mose specifically: On this side there arte differenet timings: 1,3,7,14 or 21 days per move. If you don't move within this time you lose. But then there is a timebank a time you can use once. And then if it is not a tournamnet or clan league game, if your opponent doesn't click the skull the game sgoes on.
Oh and everything is explained in teh ferquently asked questions (FAQ), that you find clicking on helo in the upper right side.