Check out Pay per Play

There are many ways to earn money from hosting a website. As seen on this one, it's littered with Google Ads (Adsense), and every click is generating revenue for the individual or company hosting these ads. The statistics can be broken down into 2 main parts. First you have your "page impressions" (number of times the page holding the ads is viewed), and secondly the number of clicks on the ads. Together they form a ratio known as the "click thru rate", which tells you what percentage of people who come to your website actually click on your Google Ads. Usually, the click thru rate is somewhere between 0.01 and 2 percent, any higher and Google starts getting suspicious. What that ratio is telling you is that you are earning revenue from 0.01 to 2 percent of the people that visit your website.