However, a search engine is simply one kind of search tool.
Search engines are databases of information about web pages.
When you use a search engine, you are searching a database about web pages that the search engine compiles and maintains. Databases are not always current and none of them includes the entire Internet. However, the information in the databases can be outdated, repetitious, skewed and it usually comes to you unclassified. Their success at this is still somewhat mixed. The most successful and advanced of these sites is the Google search engine.