Peerfly is one of the most popular CPA networks and one of the easiest to join. CPA, in case you don’t know, means Cost Per Action.
Most affiliate marketing is built on this model whether you’re promoting products from Clickbank, Commission Junction or any other affiliate network. You get paid when someone completes an action. In the case of affiliate marketing, that action occurs when someone buys a product through your affiliate link.
In CPA networks, more services than products tend to be available for promotion – mobile games, insurance quotes, dating services, etc. Promotion of these programs can be more restrictive too. You may only be able to promote some … 
