Checkpoints in Diablo 3 is a point in game where your progress is saved. While you can't use these to teleport elsewhere, you can use a Waypoint to teleport TO a checkpoint. In Diablo 3, the developers have tried to make it feel more dangerous to be out adventuring, and will limit Town Portals as well as easy travel between levels. The Checkpoint system is a way for players to easily get on with playing, without removing the sense of danger outside of towns.