It is an almost ubiquitous thing, but takes several forms technologically:
- A card stock business card which is punched out by clerks with each purchase, typically of a meal drink or event admission. After a certain number of purchases/punches, typically ten, the "eleventh is free". The card with ten punches on it is typically used as the coupon. There are also schemes which distribute stamps and let people paste them on cards that represent the rewards they want, a different number based on the value of the reward.
- A plastic stock credit card-like token that has raised type and an electronic stripe to make it easy to automatically process the card. This is common with air frequent flyer programs.
- An RFID unit
Any of these might have a barcode on it.