A subject directory is a list of web sites collected and organized by human editors.
Directories have a browseable structure.
Looksmart BUBL Link Selected Internet resources covering all academic subject areas. One way to find information in a directory is to browse. Directories also have search engines that either search their contents or the whole web. When you use Yahoo's search, you are first searching categories, web site names and descriptions. Yahoo partners with Google to then search the Google database.