What does the “@” symbol do in SQL?

Question

I was browsing through the questions and noticed this:

SELECT prodid, issue
FROM Sales 
WHERE custid = @custid 
AND datesold = SELECT MAX(datesold) 
                 


        

Answer 1

publish data where stoloc = 'AB143' 
|
[select prtnum where stoloc = @stoloc]

This is how the @ works.