what does ac mean in user stories code example

Example: acceptance criteria

what is AC-
AC are conditions which will tell us 
whether specific criterias are met so we
consider user story is DONE.


Example of AC-

As customer I should be able to pay with credit card
so I dont have to pay cash

AC-
-USER SHOULD BE ABLE TO PAY WITH VISA CARD
- ""    ""   ""    ""       ""   MASTER CARD
- ""             ""         ""   AMEX CARD

USER SHOULD BE ABLE TO PAY WITH ANY THIS 3 TYPE OF
CREDIT CARD BY ENTERING CARD OWNER NAME, CARD NUMBER
AND EXPIRATION DATE AND SECURITY CODE