OK here is what I think put in simple terms.
Its December 10th and you go to apple and purchase a product. You pay via tapping phone. In this process, a file/coupon is uploaded to your phone.
NOW here is the interesting part.
Apple chooses what time/date/location that this coupon will appear to the customer
Now following on from the hypothetical example, come a few days before December 25(boxing day) the coupon will be activated and will appear on you phone . it will show deals /coupons that apple are having for the sale.
Hope that helps.