Profile synchronization guide for Microsoft SharePoint Server 2010

This article describes profile synchronization, also referred to as "profile sync," in Microsoft SharePoint Server 2010.
A user profile is a collection of properties that describes a SharePoint user. Features such as My Sites and People Search use user profiles to provide a rich, personalized experience for the users in your organization. You can create user profiles by importing data from directory services, such as Active Directory Domain Services (AD DS). You can augment user profiles by importing data from business systems, such as SAP or Microsoft SQL Server. If users update their profiles in Microsoft SharePoint Server 2010, you can write the modified data back to directory services. The process of importing profile data from external systems and writing data back to these systems is called profile synchronization.
When you synchronize user profiles, you can also synchronize groups. Synchronizing groups gives SharePoint Server 2010 information about which users are members of which group.