In fact, directories are quite small collections of resources, compared to the huge databases that search engines search. Virtual libraries are directories that contain collections of resources that librarians or information specialists have carefully chosen and have organized in a logical way. Virtual libraries typically provide an organizational hierarchy with subject categories to facilitate browsing. The main difference between virtual libraries and directories is that virtual libraries are much smaller since the resources included are very carefully selected. Search engines are tools that use computer programs called spiders or robots to automatically gather information on the Internet and create full-text databases.
Spiders go out on the Internet and locate hyperlinks that are available to the public.
The spiders then load these resources in a database, which you can then search with the search engine. The information found on the World Wide Web is diverse and some of it may be offensive to some people or inappropriate for children. There are software programs that have been designed to block or filter Web sites that have certain words in them. There was a movement to force the government to control the content on the Web and the Internet. The U.S. Supreme Court ruled in 1997 that the Communications Decency Act of 1996 was unconstitutional in that it abridged the freedom of speech upheld by the First Amendment.