Cashback, literally "money that comes back," is a simple mechanism: when you buy a product or service from a partner retailer, part of your spending is paid back to you. You don't pay more, you simply get back a fraction of what you would have spent anyway.
A principle that's been around for a while
Some bank cards already offer rebates on your purchases. Online cashback applies the same logic to purchases made on the internet: you go through a dedicated link or app, shop normally on the store's website, and part of the commission earned by the platform is paid back to you as a balance.
In practice, this is neither an instant discount at checkout nor a loyalty point that's useless elsewhere: it's a real amount, usually in euros, that accumulates in a balance as you keep shopping.
What it changes for you
Cashback doesn't change your shopping habits at all. You keep buying from the retailers you already know, at the same listed price. The only difference is that part of that spending comes back to you, instead of staying solely with the retailer and its usual advertising intermediaries.
This is the exact principle PayHope builds on, adding one more dimension: part of the value generated by your purchase can also contribute to a charitable cause you care about, without reducing your own cashback.