This extension displays a dropdown list of any URLs that you have typed in to the Omnibox at some point, and it orders them by which URLs you visit most often (typed or otherwise). You can then click on any of the URLs to navigate to it. It only pulls from the last 30 days of history, so any URL you haven't visited in a while will drop off of the list. This functionality is similar to the old "address bar" dropdown found in past versions of other browsers. For URLs that you occasionally type in (but not often enough to make bookmarks for them), it's nice to have a list of items you can quickly pick from.