|Quoting Bill142 (Reply 2):|
you get $$ per click. How much I'm not sure.
It depends on the keyword. Advertisers buy up keywords for anything from about $0.10 to $10.00.
Google will then show an ad on the page that it feels is most relevent to your content. If someone clicks on the ad, you get a share of however much the advertiser payed for that keyword. The share you get is not known, google keeps the rest.
Google also now offers referral schemes, you will see "get firefox now" buttons on some sites, as well as buttons for Picassa, and Adsense. With the first two you recieve $1 when someone downloads and installs firefox/picassa, and with the adsense scheme you recieve $100 when the user signs up, places ads on their page and generates $100 of revenue.