Fold.it is a new project in the growing genre of human computation games, also known as crowd-sourcing. That is games that `trick’ us into doing useful computation while playing them. Fold.it uses the human brain to predict patterns in protein folding, something that is very difficult for a computer to do. From their site:
We’re collecting data to find out if humans’ pattern-recognition and puzzle-solving abilities make them more efficient than existing computer programs at pattern-folding tasks. If this turns out to be true, we can then teach human strategies to computers and fold proteins faster than ever!
For more on the science behind protein folding and how humans can help here is their about page. One previous example of this is the Google Image Labeler game. A game in which users tag random images from Google image searches. In turn the information is used to make the search more accurate.