Stages
The are multiple stages along each route in the four categories. During every stage, teams can move from one checkpoint to another (in the order you find most convenient) until you reach the "end of stage" checkpoint, where event coordinators give you the legend for the second next stage, and so on until you get to the finish. You can't visit checkpoints from previous stages after that. The only exception to this are bonus checkpoints in timed categories (Atlas, Horseman) than can be reached at any point during the game. These checkpoints deduct time from your overall time on the course and if you are planning to win, it is wise strategy to collect them.