We are often asked what the difference between a search engine and a search directory is. When a person searches for something at a search engine and a search directory, it seems as though they are the same thing. After all, you type in a keyword or phrase into a text box, click the search button and results show up. So to the casual Internet user, they seem to be the same beast. But they aren’t. In this article we explain a couple of the major differences between a search engine and a search directory.
The primary difference between a search engine and a search directory is how web sites get added to the database. In a search directory, people submit their sites, which are, in turn, reviewed by human editors. If the editor deems that the site is acceptable for inclusion based on a set of criteria, the editor adds it to the directory. Yahoo and Open Directory Project are examples of search directories.
On the other hand, search engines use spiders [small automated programs that traverse the Internet looking at web sites] to find sites. These spiders retrieve content from web sites and send it back to the search engine’s database. The search engine then analyzes the web page and ranks it according to very sophisticated algorithms, which are closely guarded secrets. AltaVista and Google are examples of search engines.
The second main difference between search engines and search directories is what gets indexed. Because search engines use spiders to find web pages, search engines index virtually any page its spiders find. Search engines typically use content found on the web page to determine the title and description displayed in search results.
On the other hand, since search directories typically involve human review of submitted websites, only the website is listed, not every page. While the submitter can suggest the title and description to use for the listing, the reviewer may change them based on how they view the website. The titles and descriptions used by the reviewer in the listing are what is displayed in the search results at a search directory.
To summarize:
Websites are added to search directories, usually by a human who reviews the submission and website before allowing it into the directory. The title and description displayed in their search results are the same as those one would find if s/he browsed the directory.
Web pages are added to search engines automatically as their spiders traverse the web through links on web pages. The title and description displayed in a search engine’s search results are pulled from content and tags found on the web page.
About.com has an extensive A to Z list of search engines and search directories.
Pandia has an interesting article about the best search directories.
