For a person to connect to SQL Server, he or she must have a login record in one of the system tables that specifies his or her login name and password. Only the SQL Server system administrator can add or remove login records.
Figure 12-2 The SQL Server security model (slightly simplified)
If you’re using integrated security, you don’t specify either the login name or the password when connecting to SQL Server. SQL Server asks Windows NT to vouch for who you are. (See “Domain managed security” on page 531.)