Advertisers are e-commerce sites, who use a network of Affiliates to generate web-traffic to their e-commerce sites.
Tracking services providers offer tracking services to Advertisers. They monitor and record visitors clicks originating in Affiliate websites and also monitor the outcomes of their visits at e-commerce sites. The tracking process matches a visitor-click and monetary outcomes that originate from such clicks, which enables them to calculate commissions and fees due to the affiliate.
Affiliates are usually special interest websites, who already have a large following of visitors, who are willing to host a banner advertisement of an e-commerce site, which might be of interest to the affiliates audience. Any clicks on a banner that takes the visitor to the e-commerce site can earn a commission or a fee for the affiiate as a reward for web-traffic generation.