Can someone please tell me who comprises the All People in SharePoint? If I have an Active Directory group that has been added to one of my SP groups, to the individual people who are in that AD group, show up as individual names in the All People list?

All People is the collection of all users with access to the Site Collection, but if they are a member of a domain (AD) group then they will show up in All People only after they have visited the site at least once. Also, while looking at People and Groups in a subsite, All People will list people who may not have access to the subsite, but they do have access to something in the site collection.Mike Smith TechTrainingNotes.blogspot.com

thank you for the clarification.

I have the same question.I found in our All People and Group list, only a small of AD users are listed there, but I'm pretty sure we have much more users have logged into the site at least once, but they are not shown in the ALL PEOPLE list.Is there a reason for that? or is some kind of action triggered to add some users in the list vs some are not added?THanks