You earn commission by promoting 'Offers' from WOW TRK. These Offers are advertising offers by third party companies. They pay for each conversion, click or sale (depending on the offer).
From the 'Offers' section in your affiliate account, you can grab banners and links to place on your website or any other traffic source you have. If a visitor then clicks on one of these banners or links and then completes the 'payable action' (listed on every offer on WOW TRK) - then you will earn commission for that action.