Comment by maicro

Based on the intonation, I'm guessing it's a "loyalty" card - it tracks your purchases, unlocks some level of default discounts, and will often accrue points you can then use for various purposes. Giant Eagle in the US is a good example - you earn points for every dollar spent, then you can redeem the points for percent off gas at their gas station, a percent off coupon, etc.

(the above description is very bland - add in anti-capitalist/m messaging wherever you deem appropriate, I won't argue)