SharePoint 2010 includes many new features that have people excited about moving to it from older versions of SharePoint or from legacy ECM systems. One of these features is a new, more powerful and flexible authentication model called claims-based authentication. Authentication is simply the process of validating a user’s identity. After a user’s identity is validated, the authorization process determines which sites, content, and other features the user can access. In SharePoint 2010, you can choose to use either ‘classic-mode’ authentication or the new ‘claims-based’ authentication.
Claims-based authentication works with any corporate identity system, including Active Directory, LDAP-based directories, application-specific databases, as well as new user-centric identity models, such as Windows Live ID.