DotNetOpenAuth.... what is?

I'm not sure what it is and what is DotNetOpenAuth. Can you explain it in few words? I am investigating about the management of users in a web application开发者_Go百科 (asp.net mvc)

From www.dotnetopenauth.net:

DotNetOpenAuth is a well established open source library that bring OpenID, OAuth, and ICard capabilities to the Microsoft .NET Framework.

So:

A .NET library, that is open source and which implements OpenID, OAuth and ICard. OpenID is the login mechanism used on StackOverflow, OAuth is a similar one as is ICard.