Here's the basics of how it works.
I have a website with a LOT of people who stop by and read articles. I'm the central focal point of dozens of small businesses. I want to send my customers to buy things from you, and in exchange, I want you to send your customers to buy things from me and my other clients. None of us are competing with each other, we're all here for each other. It's like a big, happy family that helps each other out and shares thousands if not millions of customers among each other.