Where does the internet money comes from?

This question is mostly asked by people, even people that has been online for quite a while now, and i guess you also don't know where this money comes from.
the internet is almost like the normal world where buying and selling is done, which i guess up to a certain level you would understand because we have several online stores now selling out products here online and they deliver the product to you at your door step, yeah sure this is another method of generating revenues online but that i would discuss later. Back to the topic, most of the richest online workers make their money from advertisement, How does Google make money? Surprisingly, 97% comes from advertising, the way Google made its money is the same way Twitter and Facebook will make their money," Holmes explained. how does this works? where is the money coming from? the same way you pay to advertise your product on television and radio is the same way you pay these social media owners to advertise your product so this is how they make huge amount of money, so basically any website that can generate a good amount of visitors or members can also generate revenue from advertising, all you need is to make people interested in your website or blog but before that you must understand certain things,There are four basic revenue models that you will encounter in dealing with ad networks
and advertisers. To firmly grasp their potential, you need to understand the differences
between them and how they work.
You should not confine yourself to just one model. Instead, you should consider what will
work best with your chosen site and blend the different strategies to achieve optimal
results. This may require some experimentation.