Every Google user probably has an answer for this question, and the differences among those answers are limitless. It is interesting to hear what Cutts himself has to say on the subject though, considering he has kind of become the unofficial posterboy for giving webmasters information about the inner-workings of the world's most popular search engine. Matt says there are actually a lot of things he would like to see added to Google Search, but one thing comes immediately to mind for him. When you do a search on Google (for example for "flowers"), the URL you get for the results is not just www.google.com/search?q=flowers. There are always other parameters such as "hl=en" and others. It's interesting to look at the comments for Matt's video.