Azure Active Directory Sync is the new synchronization service that will allow customers to do the following:

• Synchronize multi-forest Active Directory environments without needing the complete feature set of Forefront Identity Manager 2010 R2.
  
  
• Advanced provisioning, mapping and filtering rules for objects and attributes, including support for syncing a very minimal set of user attributes (only 7!)
  
  
• Configuring multiple on-premises Exchange organizations to map to a single Azure Active Directory tenant