what is a Search Engine

A search Engine is a document retrieval system which helps to find information on the world wide web.it is a system that gives the required info we need by searching from huge data base on web.The search results are usually presented in a list of results and are commonly called hits. The information may consist of web pages, images, information.Search engines use regularly updated indexes to operate quickly and efficently.
when we think of search engine the thing that comes to our mind is "google"
arguably google is now the search engine gaint
Google is the most used internet search engine in the world since 1998 it has indexed more than 15 billion webpages .
various search engines
1)google

2)bing
3)yahoo
4)Wolfram Alpha
5)Alta vista
6)ask.com
7)cuil,etc
Search engines are very crucial to the web user.it makes task easy for user.
with an estimated over 29.5 billion webpages(feb 2009) finding the thing u want is like finding a ring dropped in ocean.
search engine results are displayed as
*links
*orderly arranged in terms of relevancy to query
*recently used mostly accessed

hope this information is helpful to you.