RAISERROR() 的语法含义是什么

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

Create trigger tgrInsteadTrigger on copytableto
Instead of Insert as 
    Declare @store_name varchar(30);
    declare @sales int;
    declare @date datetime;

    select @store_name = i.store_name from inserted i
    select @sales = i.sales from inserted i
    select @date = i.Date from inserted i
begin
    if (@sales > 1000)
        begin
        RAISERROR('Cannot Insert where salary > 1000',16,1); ROLLBACK;
        end
    else
        begin
        insert into copytablefrom(store_name, sales, date) values (@store_name, @sales, @date);
        Print 'Instead After Trigger Executed';
        end
End

在上面的语法中，我使用了 RAISERROR('Cannot Insert where sale > 1000',16,1)

RAISERROR('Cannot Insert where salary > 1000').