Commission Junction is a performance based affiliate program. You can sign up for the Commission Junction affiliate program, select the merchants you would like to advertise for, and place their advertisements on your web site. CJ online takes care of tracking the commission you are owed and paying you. They, in turn, provide reports to the merchants to help them capitalize on their pay per click advertising campaign. They will also work to resolve any conflicts between you, the publisher, and the merchant.
Networks like the Commission Junction network typically offer a lot of guidance to both the merchant and the publisher. The more money you make and the more sales the merchant makes, the happier everyone is.