One way Google makes money is from advertising. People and companies will come to Google and pay for their ads to be shown throughout the web. Google, then, gives people the choice to place the ads on their website. Depending on the type of ad, Google will pay you a portion of the money that they were paid by the advertisers per click or per view.
For sites like Hubpages, as you write articles, Hubpages will place google ads on your article page and, if you have linked your Google account with your Hubpages account, as people view and possibly click the ads on the page, you will be paid by Google. In order to make a lot of money, though, you will need to maintain a consistent stream of hundreds of views.