A computer software program designed to help the user find information on the World Wide Web. A search engine is a searchable database which collects information on web pages from the Internet, and indexes the information and then stores the result in a huge database where it can be quickly searched. The search engine then provides an interface to search the database.
"...More recently, computer software designed to help the user locate information available at sites on the World Wide Web by selecting categories from a hierarchical directory of subjects (example: Yahoo!) or by entering appropriate keywords or phrases (Google, Hotbot, etc.). Most Web search engines allow the searcher to use Boolean logic and truncation in search statements. Results may be ranked according to relevance or some other criterion..." ODLIS
 Parts of a Search engine
A Search engine has three parts.
• Spider: Deploys a robot program called a spider or robot designed to track down web pages. It follows the links these pages contain, and add information to search engines’ database. Example: Googlebot (Google’s robot program)
• Index: Database containing a copy of each Web page gathered by the spider.
• Search engine software : Technology that enables users to query the index and that returns results in a schematic order.
 Types of search engines
In broad sense, search engines can be divided into two categories.
1. Individual search engines
An individual search engine uses a spider to collect its information regarding websites for own searchable index. There are two types of individual search engines.
2. Meta search engines
A Meta search engine searches multiple individual engines simultaneously. It does not have its own index, but uses the indexes collected by the spiders of other search engines.
 Advantages of using search engines
Search engines are best at finding unique keywords, phrases, quotes, and information buried in the full-text of web pages since they normally index WWW documents word by word.
Search engines allow the user to enter keywords, and then they are searched against its database. Users can use advanced search techniques such as phrase searching, truncation/wildcard searching, as well as for Boolean operators (AND, OR, NOT combinations).
With comparison to web directories, search engines are huge databases and contain a large amount of materials. Also, the database is updated at a variable rate.
- Ranasinghe, W.M.T.D. (2006) Search engine: an effective tool for exploring the Internet. in MULTIINFORM Library, Eastern University of Sri Lanka. Available on: http://eprints.rclis.org/archive/00007606/
edited by: W.M. Tharanga D. Ranasinghe, Assistant Librarian/User Education Services & IT, University of Kelaniya, Sri Lanka. Blog