MS SQL Server can operate in two security modes: Windows Authentication (Windows logon) and Mixed Mode (Windows and SQL Server logon).

In Mixed Mode, you can logon to an instance of the SQL Server through a Windows NT or SQL Server user account. Logging on with a Windows user account will allow you to use trusted connections. After logon to the SQL Server, the security mechanism works the same in both modes.

SQL Server logins employ user names and passwords and are easier to manage than a Windows NT system of users and user groups, especially for non-critical data. In such cases, you can create only one SQL Server user account for all users, but you will not be able to track individual user activity.

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Windows Authentication

SQL Server Authentication

Creating Server Logins

Fixed Server Role

Fixed Database Role

SQL Server Service Settings