Microsoft Azure Active Directory Connect (Microsoft Azure AD Connect) is a tool that connects on-premises identity infrastructure to Microsoft Azure Active Directory.
Azure AD Connect guides organizations through Azure AD integration with local directories and streamlines the process so fewer tools are required.
Prior to the release of Azure AD Connect, enterprises that wanted to combine on-premises Active Directory accounts with cloud-based Azure AD services needed to use DirSync and Azure AD Sync Services. Azure AD Connect combines the previous two tools and, according to Microsoft, connects an on-premises Active Directory to a tenant in Azure AD in four steps. Azure AD connect also reduces the on-premises footprint, eliminating the need to deploy multiple servers.
Azure AD Connect became available for public preview in December 2014, and will be released for general availability in June 2015.