It searches for any auction that has any word that starts with "fold" (folding, folder, foldable, fold, etc.) within the Cycling category that can be shipped to the US. This picks up European and Asian sellers that are willing to ship to the US. Unfortunately, this also picks up a number of items that have "fold" words that are not necessarily folding bikes, but it does give a good number of bikes without having to do multiple searches.
I use the * as a wildcard so that I don't have to type in tire and tires. It'll handle any word that starts with tire. That will take care of most any oddball items that will pop up in a search. There doesn't appear to be a need to search for bike and bicycle as long as you're looking in the Cycling category.
Conversely, it might also be good to search "All Categories' instead of limiting the search to the intended area. Sometimes there are miscategorized bargains to be found that way...
Oh... I completely agree. I do search all categories sometimes too. You never know when someone is going to slip up and post something in the wrong category. I don't do it often, but I agree that it's valuable to check that way too.