Ads on the marketplace goes by Cost-Per-Click (CPC) bidding model by default. This is the easiest way to leverage on the marketplace and no technical requirement is needed.
Listing ad on the marketplace is free, if there is no click to the ad, there is no charges at all.
We've also introduced a Premium Hybrid Ad (also known as Enhanced CPA/CPL) for more IT savvy advertisers who can implement conversion tracking. Running Premium Hybrid Ad is on case-by-case basis, please contact us for assistance.