In SQL Server Management Studio what is SQLCMD mode?

Question

In SQL Server Management Studio I would like to know what is SQLCMD mode?

Answer 1

Message Transact-SQL IntelliSense is not active for this editor because the editor is in SQLCMD mode.

I was publishing SQL Server Project from Visual Studio to Database to synchronize changes and got an error above. Publishing was failing. I closed all open files in VS and it resolved the issue.

I hope real life example explained why people use SQLCMD mode.