If you consider traditional media, a business might have to pay $1,000,000 to have a television ad produced and shown on TV. There is no guarantee that the ad will result in sales, and so they are risking a lot of money for an unknown result.
With internet marketing, the same company can take their $1,000,000 budget and simply offer a portion of it to anyone who makes a sale. The sale has to be made before they pay anything, so it's a guaranteed result. That's why almost every major brand and retailer now has a partnership program.
With nothing more than a laptop and a bit of creativity - anyone can build up an audience of people who are interested in any subject imaginable. The bigger the audience, the more money you can make by partnering with products and brands that are aligned with your audiences interests. Help your audience find out about great new products and whenever they buy something you make money!
With social media, everyone can start their own little advertising company.
Once you're setup, you will get a special link to put on your website. When people click the link a 'tracking cookie' is stored on their computer that will confirm that they came to your site before they bought anything and you can check it online. The tracking systems are 100% reliable because the advertisers really want to make sure they reward people who make sales so that they will make more!