It's a search engine launched by a startup of ex Google managers from California. Cuil has already indexed more than 121 billions pages, [chech your site, probably it already is in Cuil cobweb ;) ]
Founders: Tom Costello and Anna Patterson, respectively husband and wife.
Some examples: Search Make Money Online in Google, today there are 37,300,000 results, then search the same keyword in Cuil and you'll find 129,471,257 results for Make Money Online. Another one, Make Money Business, in Google: 27,900,000, and in Cuil: 25,988,369 - an overturning of numbers. What does this mean? Apparently, Google is more selective for determinate key than Cuil, which doesn't have a pagerank. What standard of judgement use Cuil in order to position a web site? It's not so clear yet.
An important thing that could make the difference, Privacy. Cuil do not stores up users traces about their researches.