Hi there
One of the ways a lot of us on this forum make money is by creating sites or blogs on topics that interest us. We write useful content and then affiliate ourselves with other companies that sell products that relate to our theme.
For example I have a fitness site that tells people how to flatten their stomach. I offer a ton of free information and draw in traffic from the main search engines. Then I refer my audience to books and programs that relate to my theme and I earn a commission for anything sold through my referral.
If you want to learn how this works I would download Make Your Content PREsell. (It's free.)
http://mycps.sitesell.com You don't have to buy Site Build It! as the book suggests but read through the book so you can learn more about how to make money by just building a site on content.
When you're done let us know if you have more specific questions. I think the book will give you a nice overview.
That's one way of making money online and in my opinion the most convenient. It's the only way I've ever done it and has worked out well.