You configure access to SQL Server using server logins. You can configure various levels of access to these logins:
By the roles to which those logins belong.
By permitting access to specific databases.
By allowing or denying object permissions.
Just as there are two authentication modes, there are also two kinds of server logins. You create domain logins using domain accounts, which can be domain or local user accounts, local group accounts, or universal and global domain group accounts. You create SQL Server logins by specifying a unique login ID and password. Several logins are configured by default, and these include local Administrators, local Administrator, sa, NETWORK SERVICE, and SYSTEM.
To narrow the scope ...