Affiliate Networks are sites that specialize in marketing and cater to both the advertiser and the publisher. They manage the affiliate programs for a large variety of businesses, products & services.
With Affiliate Networks, the Advertiser is the company that hires the network to handle a portion of their advertising through the use of affiliate programs. The Publisher would be you, the affiliate.
Most Affiliate Networks require you to have your own website. They depend on you, the publisher, using your site to help generate traffic to their advertisers' sites and supply you with an array of advertising material to help ensure your success. Here are a few of the more popular Affiliate Networks: