The program, part of Google Labs, works like this:
This experiment lets you influence your search experience by adding, moving, and removing search results. When you search for the same keywords again, you’ll continue to see those changes. If you later want to revert your changes, you can undo any modifications you’ve made.
At the moment the results of the program will only be stored per user and not applied to the general search index, so that sites buried (“I don’t like”) will not appear in future results for the user, where as sites voted up will stay up. Google Labs notes that “this is an experimental feature and may be available for only a few weeks,” still, who would have thought that Google would even experiment with Digg style social voting.
Screen shot below directly from the programs site here.