A set of permissions.
In Oracle it is important to note that roles are disabled in PL/SQL run with definer rights. In PL/SQL permissions must be granted directly or invoker rights can be used in the block by adding the phrase
In SQL Server "All versions of SQL Server use role-based security, which allows you to assign permissions to a role, or group of users, instead of to individual users. Fixed server and fixed database roles have a fixed set of permissions assigned to them."