AdSense is a hybrid of Google`s Webmaster advertising program called AdWords. In a nutshell, Webmaster are paying Google to promote their ads on Google.com. Every time an ad gets clicked, Google deducts a pre-determined amount from their advertising budget.
You can see these AdWords ads by doing almost any search on Google and the ads show up in the far right-hand side of the page. See the screenshot below:
Then Google pays us, the publishers, a certain percentage of what the AdWords customers are paying Google for those ads. In other words, as an AdSense publisher, you are helping Google advertise these AdWords ads, and Google is paying you a share of the revenue they earn every time your visitors click on your ads.
The increase the chance that people will click on your ads and of course that just means more earning for you. Google will never disclose how much you will earn per click, but you can earn anywhere between 0.01 and $10.00 per click, and perhaps even more. Keep in mind these numbers are just estimates. Google has never supplied any specific data on how much you can earn. They keep this kind of information very close to the vest.
So, once your account reaches $100.00, Google sends you a check. And you can even have them direct deposit the check right into your bank account.