ShareASale is a large and well known Affiliate Network and it has been in business for 19 years, exclusively as an Affiliate Marketing Network. Their technology receives accolades for speed, efficiency, and accuracy and they are famous for their fair and honest business practices. It has well over 3,000 advertisers and merchants. You can join these merchants and promote their products via text links, datafeeds, banners, coupons/promotional codes, etc. and get paid for it.
The amount of money you earn depends on what the specific merchant, which you selected to advertise on your website, is offering to pay you. It could be a percentage of a sale, a fixed rate per sale, a fixed rate per lead, etc.
This Affiliate Network is highly recommended by for both Publishers and Merchants.