Search Engines vs. Directories
How Search Engines Work - Search Engine Watch

Directories are hierarchically organized indexes created by people. All the sites listed in a directory are organized into rough categories similar to the way that business are listed in the yellow pages of the phone book. Directories allow you to browse through lists of Web sites by subject. They are selective in terms of what sites are included, in that every site included in a directory has been evaluated by a person. Directory databases tend to be smaller than those of search engines.

Often, there are fewer “hits” for your search, but, chances are, those hits will be more relevant because they were selected and categorized by people, not by a machine. One example of a directory is the Open Directory. Some search engines, such as Yahoo, which originally began as a directory, also have directories.

Search engines are created by computers called “crawlers” or “spiders” that churn through the web to create a database of Web pages. When you search for a specific word or phrase, search engines will return a list of Web pages to you based on the words they have indexed. Your search results will differ depending on which search engine you use. Factors that influence results include the size of the search engine’s database (i.e. the number of sites it includes), the frequency that it is updated, the search capabilities and algorithms of the search engine, and what part of web pages the spiders indexed (for example title, title and first few paragraphs, meta tags, the whole document). Examples of search engines are Google, Bing, and DuckDuckGo.

Directories tend to include fewer sites than search engines, but the sites are better organized. Directories tend to be most useful when searching for sites that you know exist and you want to find quickly, for example a company site like Ford Motor Company, or for searching for a broad subject area. Search engines are bigger than directories, but finding what you’re looking for with a search engine can sometimes be a challenge. If you are looking for any and all references to a search term, such as a product or a person’s name, or are searching for something very specific, you would be better off using one or more of the search engines.