A search engine is a tool which is design to search any information on the web. When you search any word on any search engine then search engine displays the results in the form of list. The information may consist of webpage, image or any other type of files. On a search engine most search queries are relatively simple. Some search engine also sees data into the database or opens directories. Search engines works algorithmically or are work with mixture of algorithmic and human input.
There are many search engines available on the web like Google, Yahoo, Bing, Search Spry, Baidu, MSN, etc. Any search engine works on following order.
1. Web Crawling
2. Indexing
3. Searching
Search Engine works by search the webpages on web itself and stores it. These webpages are searching through a web crawler. Web Crawler is also known as Spider. Web Crawler is an automated web browser which follows every link which it sees. Then content of each web page is analyzed for determine that how index this page. The content analyzed through its heading, title, and special fields such as Meta tags. Then data about webpages are stored in an indexed database, which is used in later queries. Some search engines, like Google, stores part of the source page as well as information about the web pages, whereas others search engine like AltaVista, store every word of every page they were find. It can be very useful when the content of the current page has been updated that this pages always holds the actual search text since it is the one that was actually indexed, so when the content of the current page has been updated it can be very useful.
There could be a problem that it is not necessary that search engine crawl daily our webpages then in that case if we change the information on the webpages still search engine displays result list according to the old information it stored.
When a user enters a word want to search into a search engine, the engine analyzes its index and provides a list of web pages which is best-matching to the word according to its criteria. Normally it also provides a short summary containing the webpage's title, headline and sometimes parts of the text.
Success of a search engine is based upon the relevance of the result set it gives back. While there may be millions of webpages having same keyword, some webpages may be more popular, more relevant than others. Which pages are the best matches, how a search engine decides, and what should be the order to display results to shown? It varies widely from one search engine to another. Over time the methods also change as internet usage changes and new techniques evolve.