Universal containers uses an Employee portal for their employees to collaborate.

The role of Active Directory in this scenario is an identity provider. An identity provider is an application that authenticates users and provides information about them to service providers6. A service provider is an application that provides a service to users and relies on an identity provider for authentication6. In thisscenario, the employee portal is a service provider that provides collaboration features to employees and relies on Active Directory for authentication. Active Directory is anidentity provider that authenticates employees using their corporate credentials and sends information about them to the employee portal7. References: Identity Provider Overview, Configure SSO to Salesforce Using Microsoft AD FS as the Identity Provider