SQL Server: Null VS Empty String

Question

How are the NULL and Empty Varchar values stored in SQL Server. And in case I have no user entry for a string field on my UI<

Answer 1

NULL is a non value, like undefined. '' is a empty string with 0 characters.
The value of a string in database depends of your value in your UI, but generally, it's an empty string '' if you specify the parameter in your query or stored procedure.