Yes, it does, and yes, they do -- if you're making any for them. Just having the ads on a web page that never gets any hits doesn't do anything; people (other than you) need to be visiting your site. And you do need to be over the payment threshold before they'll pay you anything -- see the AdSense terms for more information. It's not a get-rich-quick scheme by any means; think of it as a way to help pay for maintaining your site at best. If your site really takes off, there is the chance that you could make a not-insignificant advertising income from AdSense, but don't make that your business plan going in -- the average AdSense publisher (mostly people with low-traffic, content-free blogs who were hoping to get money for nothing) waits a very long time to see any return on their ten-minute "sweat investment". If you can't provide the eyeballs and the clicks to the advertisers, they won't pay Google and Google won't pay you.