Auto-advance is a sim league setting that moves the league forward on a timer, so nobody has to press a button for each day and the league keeps a steady pace through the season.
In HoopSim the commissioner turns on the auto-commissioner, which advances a set number of league days, 1 to 7, on a regular cadence (24 hours by default) during the game phases. The commissioner also sets how many GMs must be marked Ready before a run goes ahead; a new multiplayer league starts at 100%, so the league advances on consensus, and Ready flags clear after each advance. The commissioner can pause it, skip a run, or advance early. In the offseason, autopilot does the same for the phases between seasons. A solo league never uses it: the one GM advances by pressing SIM.
Rulebook: How the league advances. Related: sim day, commissioner.