Online, I got a laptop to pick up in the market, and online is what cashback of 50 euro but I do not know what exactly that is. The laptop was not on offer, so I'll pay 50 euro less?
You pay the full price and get 50 euro back. It can also be that they give you in the form of a coupon. Is in the small print.
At Cashback you either get the discount deducted in the cart or you have to register the device with your invoice at the manufacturer and get the money transferred from the manufacturer to the account.