The point is to trigger a donation of 20 grains of rice for every multiple answer vocabulary question you answer correctly on the site. The rice is paid for the advertisers at the bottom of the page. And how does it reach those in need? From the site's FAQ:
The rice is distributed by the United Nations World Food Program (WFP). The World Food Program is the world’s largest food aid agency, working with over 1,000 other organizations in over 75 countries. In addition to providing food, the World Food Program helps hungry people to become self-reliant so that they escape hunger for good.
Other similar sites, on which a donation is made with nothing but a click, include thebreastcancersite.com and theanimalrescuesite.com. Look across the top of either site for even more.