There are 3 types of Authentication. Windows, Forms and Passport Authentication.
Windows authentication uses the security features integrated into the Windows NT and Windows XP operating systems to authenticate and authorize Web application users.
Forms authentication allows you to create your own list/database of users and validate the identity of those users when they visit your Web site.Passport authentication uses the Microsoft centralized authentication provider to identify users. Passport provides a way to for users to use a single identity across multiple Web applications. To use Passport authentication in your Web application, you must install the Passport SDK.