What is the syntax meaning of RAISERROR()

Question

I just created a Instead After Trigger whose syntax is given below:

Create trigger tgrInsteadTrigger on copytableto
Instead of Insert as 
    Declare @store_name         


        

Answer 1

according to MSDN

RAISERROR ( { msg_id | msg_str | @local_variable }
    { ,severity ,state }
    [ ,argument [ ,...n ] ] )
    [ WITH option [ ,...n ] ]

16 would be the severity.
1 would be the state.

The error you get is because you have not properly supplied the required parameters for the RAISEERROR function.