What is Federation? ( Digital)

Digital Federation
What is federation in simple terms

Federation - I compared it with the References in your Resume or References you give to your friends saying this restaurant is good, this place is good etc.
How it is related? Its based on the "Trust". The References in the resume is trusted by the hiring manager, or your friend trusts your suggestions/comments and goes to that particular restaurant/place.

In business & IT terminology, Enterprise Federation is about making two Enterprises come toghether and share their user information/attributes.i.e Enterprise A sends user information/attributes to Enterprise B by asserting (SAML Assertions) that it knows the user. Here, Enterprise B trusts Enterprise A ( there will be a trust relationship already existing) on a certain trust level and accept the user information/attributes sent. Its now upto the Enterprise B to decide what level access it can give to this particular user. The same way your friend might/might not go that particular restaurant/place.