For those who did not have tops in English it is good to explain that translated, contest advertising means "contextual advertisement".
This means that you will have the opportunity to include banner ads with arguments related to your site.
For example, if you own a pet site, you can include banners about kennels, leashes, etc etc ...
This is important because if a visitor enters a pet site, it is hardly attracted by banners selling hydraulic valves: there is therefore a greater chance that a user is pushed to click.
The gain comes from the clicks that users make on these banners (this is a very similar method to pay per click, the only difference is the advertising contextualization).
Evaluate which of the sites you offer most to your case (in terms of wages, banners available, traffic quality, ...) because our advice is to subscribe to 2 or 3 services in order to accumulate more money in the same port to reach faster payout.