单选题 The Internet is not an ordinary encyclopedia, i. e, an organized knowledge database. The Internet is more like a disorganized database to which everyone can contribute. Because of the diverse and widespread information when one needs it, there is a need to bring some sort of organization to the Internet community. Today, there are web directories and search engine as two of the most useful mechanisms responsible for bringing order to the Internet.
Web directories organize links to many places on the Internet where information about a specific topic can be found. Web directories can have a general or topic specific focus and are usually organized into several categories based on the topic specific focus. Web directories are good sources of information if they are well-maintained with regular updates. They are usually maintained better by human software.
Search engines are yet another tool that helps you find information on the Internet. There are many search engines on the Internet but the biggest and the most popular are Google, AOL Netscape, Lycos and MSN.
Search engines, however, are different from web directories. They do not categorize links to web places like web directories do but they allow users to "search the Internet" using specific search terms. However, it should be noted that what is really being searched at the moment you submit your inquiry (in the form of a search term) is, in fact, a database. There databases are constantly updated and upgraded with so called "search engine spiders" which search the Internet all the time looking for new and recently updated websites.