A Program is a period of time where laps and mileage are tracked. For example, if creating a program for the entire new school year, set the start date of the program to the beginning of the school year and set the end date after the school year is complete.  Just be sure the dates cover all scanning sessions.
You can have multiple programs running at the same time (pun intended).  For example, you can have programs for a Morning mile session before school, Mileage Club at noon and a one-time fun-run fund raiser. Just create a program for each event to keep the mileage separate.