Built-in and custom implementations of ASP.NET's Role Provider, as part of Membership functionality in the System.Web.Security namespace.
ASP.NET supports user authentication and authorization through a provider-based model. In support of the authorization providers, there is a Role Provider which supports filtered access to resources by checks against pre-assigned roles.
MSDN Documentation
Managing Authorization Using Roles
Questions for this Tag
Questions that should have this tag pertain to use of the default ASP.NET Role Providers (AspNetSqlRoleProvider & AspNetWindowsTokenRoleProvider), as well as questions about extending/overriding the built-in provider.