What is the difference between login and user in SQL?

What is user and login in SQL Server?

A Login is used for authentication into a SQL Instance while a User is used for authorization into a SQL Database. Note that Logins are used at the Instance level and Users are used at the Database level.

How do logins differ from users?

A "Login" grants the principal entry into the SERVER. A "User" grants a login entry into a single DATABASE. One "Login" can be associated with many users (one per database).

What is SQL user without login?

The WITHOUT LOGIN clause creates a user that isn't mapped to a SQL Server login. It can connect to other databases as guest. Permissions can be assigned to this user without login and when the security context is changed to a user without login, the original users receives the permissions of the user without login.

How do I login as user in SQL?

To create a login that is saved on a SQL Server database, select SQL Server authentication. In the Password box, enter a password for the new user. Enter that password again into the Confirm Password box.