The ASP.NET membership system is primarily designed to be used with ASP.NET login controls and with ASP.NET Forms authentication. That is, the membership system is most useful in applications where you get user credentials in your application and need to validate them. However, you can use ASP.NET membership with any custom authentication system.
Windows and Passport Authentication
In ASP.NET Web applications, you can also use Windows authentication or Passport authentication. In Windows authentication, your application does not need to perform authentication; Windows validates user credentials when the user accesses a Web application that is configured to use Windows authentication. You can access the user-identification and authentication status with the class. In Passport authentication, user credentials are validated against a centralized store available to any Passport-enabled Web site. You can get the user's name and authentication status using the class.
For more information about selecting an authentication strategy, see ASP.NET Authentication.
Managing Users by Using Membership