Azure AD Connect
The Azure AD Connect software is freely available from Microsoft and is used for synchronizing local Active Directory infrastructures with the Microsoft Azure Active Directory. The previously available software “Dirsync” is no longer supported.
Azure AD Connect automatically creates and updates local Active Directory users and groups in Azure Active Directory. Creating and editing new users and groups in Azure AD is therefore only intended for “online only” users (i.e. users who are only created in Azure AD and do not have a user account in the local Active Directory structure). There are also advanced settings that allow synchronization of multiple local domains and forests with Azure AD.