The externalized authentication provider is generally defined as the Identity Provider (IP) and often publishes a Security Token Service (STS).
The application or software solution externalizing the authentication process is called Service Provider (SP) or Relying Party (RP).
The consumer, who uses the SP authenticating with the IP is generally called the Subject
Web Services Federation Language 1.1 (WS-Federation): “defines mechanisms to
allow different security realms to federate, such that authorized access to resources managed
in one realm can be provided to security principals whose identities are managed in other
Active Scenario (SOAP-oriented) is used by SharePoint 2010 in the service applications’ communication infrastructure.
Web browser based scenario, SharePoint and web/HTTP
Sequence diagram of WS-Federation for the Passive Requestor scenario.