Have fun and help Google improve it's image search results relevance, so that other Google visitors can get accurate search results. When you press the Begin button on the page, you'll be randomly paired with a partner who's online and using this feature.
Then over a 90-second period, you and your partner will be shown the same set of images and asked to create as many labels as possible to describe each image that's displayed. When the labels match, you earn points and move on to the next image until the time expires. After the time expires, the images you've seen will be displayed with link to the web sites where they can be found.