Logins
Login identifiers (Ids) are associated with users when they connect to Microsoft® SQL Server™ 2000. Login IDs are the accounts that control access to the SQL Server system. A user cannot connect to SQL Server without first specifying a valid login ID. Members of the sysadmin fixed server role define login IDs.
sp_grantlogin authorizes a Microsoft Windows® network account (either a group or a user account) to be used as a SQL Server login for connecting to SQL Server using Windows Authentication. sp_addlogin defines a login account for SQL Server connections using SQL Server Authentication.