It’s how they are able to run their platform without monetization and ads. They give you (the user) a certain balance at a certain time with a deadline and you can, but don’t have to, send the tokens over to the sites you want to support.

The sites receive the tokens and can now (eventually) be funded without annoying their viewers or customers with bullshit ads popping up left and right. This is possible because the BAT tokens (received from supporters) can be used as a means of currency or even be exchanged for fiat.