The Acceptance (or commitment) lists are the original entries for each tournament.  They give an idea of who will be at the events.  Acceptance lists for futures and satellite events will be available 1 to 2 weeks prior to the event (keep in mind that for these events, entries close 2 weeks before the event).

Acceptance lists are not available for ATP events or challengers at this site.  For ATP events, you can visit the ATP site at:
http://www.atptennis.com/en/media/entrylists.asp

If you are interested in other sources for ATP or challenger entry lists, let me know and I will try and point you in the right direction.