A web search engine is an interactive tool for locating information available via the World Wide Web. Web search engines are actually databases that contain references to thousands of resources. Each search engine provides its own database, interface, and special features. The hypertext environment makes it possible to offer a link directly from a list of results to the resources themselves.
Most search engines use automated tools and programs to gather resources.
These tools, often referred to as worms, spiders, crawlers, and robots, search thousands of websites worldwide, collect information, and then store the information in the database. A search engine's database cannot be all inclusive of the WWW, therefore search results will not include every available web resource. Additionally, because each search engine collects resources differently, the same query typed into different search engines will likely produce different results. A web meta-searcher is a tool which provides access to multiple search engines from one location. It enables a user to more efficiently obtain search results from several databases by typing in a single query.