A directory can refer to two main things, first is a folder that contains a "table of contents" on a floppy or hard disk. Second is a website such as Dmoz or Yahoo, that contains a list of websites in relevant categories like health, entertainment, computing, business, sport, recreational, food, education and shopping. Some directories charge for a listing, Yahoo used to charge £150 for your site to get reviewed in a fast time frame (it could take months if you were lucky otherwise. Otherwise directories can change a smaller amount for money for a review or ask for a link back request to generate traffic for the directory. At the moment directories currently seem out of vogue and Yahoo have all but given up concentrating on it, and have instead seen more revenue available in search listings. Dmoz is perhaps the best know directory on the web, and accepts volunteers to edit categories. It has become such a mammoth task that they have thousands of editors, and even include categories for small towns all over the United Kingdom.