Most Click-to-Donate sites opperate in the same way.  A user performs a click that refreshes the page creating ad impressions.  Those impressions are then sold to advertisers and the site donates proceeds to charity.  Some sites will also offer donations in exchange for some sort of promotion of the site itself - typically in the form of a Facebook like or a tweet.  My favorite Click-to-Donate site is Care to Click .

Great web video that explains how Click-to-Donate sites works.

Community content is available under CC-BY-SA unless otherwise noted.