Search engines are computer programs that search for words or phrases in internet documents.
Search engines vary widely in how and what they search. Robot searches tend to retrieve both a larger number of documents and a greater percentage of irrelevant documents than search engines which rely on the evaluative powers of the human mind. The key is to analyze your search results using your own evaluative powers. How Search Engines and Guides Work Subject Directories Subject directories or guides are search tools that are created by people. Web-sites are submitted, evaluated, and arranged into hierarchical subject categories.