From their site:

Performance Marketing is one of the most powerful and effective customer acquisition tools available to an online Merchant. As a Merchant – you decide the commission structure to pay – and only pay when results come in.

Established in 2000, ShareASale provides award winning technology and service which will enable you to connect with a network of established Affiliates as well as recruit new ones to your program.

There are currently over 2,000 Merchants plugged in to the ShareASale Network. Each of these merchants has a different type of product that they are selling – and each is ready to commission you on that sale if you bring a customer to them.

The idea – and the implementation – are simple. You decide which merchants to promote and how to promote them, and when commissions are generated, you can see your stats in real-time. All payments are consolidated from the programs you participate in, and are paid with one check or direct deposit by ShareASale.