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
https://msdn.microsoft.com/en-us/library/azure/dn790204.aspx?f=255&MSPPError=-2147217396