According to Microsoft :
http://technet.microsoft.com/en-us/library/cc784710(v=ws.10).aspx
What does Access-based Enumeration do?
Access-based Enumeration filters the list of available files and folders on a server to include only those that the requesting user has access to.
Who does this feature apply to?
This feature applies to:
Domain-joined computers.
IT professionals who want to control the user’s experience.
In normal language :
When using Access-based Enumeration, a user only sees the files and folder it is allowed to see.
Example :
A user is a member of the group Finance and Office, but not a member of the group Sales.
He only sees the folders Finance and Office, but not the Sales folder, and it contents.
A User is a member of the sales group, he only sees the sales folder and nog the other files and folders.
Actual folder contents