Security Assertion Markup Language 2.0 (SAML 2.0) is an XML-based, open-standard data format used for exchanging authentication and authorization data between a Service Provider and an Identity Provider.
It uses security assertion tokens to to pass information about the end user between the identity provider and the service provider.
SAML 2.0 enables web-based authentication and authorization scenarios including cross-domain single sign-on (SSO).
For more information about SAML see the Oasis documentation