SQL Server, connecting without windows authentication? I am confused about how this works:
I was reading the SQL Server documentation on authentication here:
Choose an Authentication Mode
It says:

Windows Authentication is always available and cannot be disabled

This makes me think that ALL connections to SQL server NEED windows authentication (as it cannot be disabled), but it goes on to talk about the advantages of having only SQL Server authentication, for example:

Advantages of SQL Server Authentication

Allows SQL Server to support environments with mixed operating systems, where all users are not authenticated by a Windows domain.


So, can you connect to SQL server without Windows Authentication or not?
Windows Authentication is always available, SQL Server Authentication is only available if Mixed Mode is enabled.


  During setup, you must select an authentication mode for the Database Engine. There are two possible modes: Windows Authentication mode and mixed mode.


So:

For an instance using Windows Authentication mode, connections can only be established using Windows Authentication.

For an instance using Mixed Mode, connections may be made using either Windows Authentication or SQL Server Authentication.

In other words, Windows Authentication being always available does not mean it is always used. A company may choose to use only SQL Server Authentication, even if Windows Authentication cannot be disabled (it will remain enabled but unused).