Search engines provide you with a search window to enter the keywords you want to find. The search engines give you a ranked list of the World Wide Web sites that most closely match your search terms. The metasearch engines then either display the search results from each search engine or consolidate the search results into one grouping.
Subject directories are selective.
They include only a small portion of the sites that you would be searching using a search engine. An active human intelligence has gathered and organized the sites. You will retrieve far fewer sites to look through and the sites are far more likely to be relevant.