There are many ways through which sales can be recorded for customers who use bank credit card or debit card.
Below are some of the ways :

1. PoS ( Point of Sale ) : These are machines which you see in any retail outlet or store where in you have to swipe the card. The machine vendor which eventually charge some 2-3% of the sales and the rest will reach your account.
2. Online : If you shop online or buy something from online you can use your card to pay using payment gateways. You can also pay trhough wallets such as Apple, Google , PayTm etc.