Security Assertion Markup Language(SAML) is an XML-based, open-standard data format for exchanging authentication and authorization data between parties, in particular, between an Identity Provider and a Service Provider. In our case, miniOrange is the Service Provider and the application which manages credentials is the Identity provider.
The SAML specification defines three roles: the Principal (in this case, your WordPress user), the Identity provider (IdP), and the Service Provider (SP). The Service Provider requests and obtains an identity assertion from the Identity Provider. On the basis of this assertion, the service provider can make an access control decision – in other words it can decide whether to allow user to login to WordPress.
For more details please refer to this SAML document.