Azure Active Directory pass-through authentication
Pass-through authentication provided by Azure Active Directory will enable users to login to cloud resources by validating their password against their on-premises local Active Directory. This feature will allow customers that can't or don’t want to store passwords in the cloud to onboard Azure AD and Office 365. They won't have to modify their corporate network infrastructure or install products such as Active Directory Federation Services (AD FS) or similar third-party federation solutions. Pass-through authentication will be available via Azure AD Connect as the third option of authentication along with Password Sync and AD FS.
Additionally, with this new update, both Pass-through and Password Sync authentication options will provide seamless SSO to Azure AD connected applications from Windows devices, as AD FS was offering until now.