The more keywords you can provide, the better chance of retrieving relevant information. This means that you can search on any word that appears on the website. Directories are different. Directory Directories are very much like a telephone book's yellow pages. In the yellow pages, businesses are listed by category such as restaurants, banks, hardware stores, etc.
Internet directories do much the same.
When you search at a directory, you are searching for keywords which appear in the title and description only. Many search sites use both search engine information and directory information to give you the best of both worlds. If you would like more technical information, or first-hand information about the history of the Internet, try the Internet Society .