Questions about saving and loading (resuming, restoring) state of the game, allowing player stop and continue playing game at arbitrary moments of real and game time.
Game saving can be different in their realisation and tend to fall in some of the following categories:
Any time exact state save: game saves state completely and restores it to exact same moment of game time.
Game save stations and checkpoints: game can be saved at specific locations or saves aotomatically at some game story points.
Diablo style 'save and exit': game is saved only on exit, and, to prevent cheating, usually some of the player progress is lost (he is returned to some checkpoint).