A search engine is a device that delivers contents to you as per your query from the World Wide Web. Search engine locates the suitable content from the plethora of information available on WWW in form of links, images and web pages. These engines are based on complex algorithms and sometimes even on human editing.

The search engines stores millions of pages of data available on the web and then uses different processes to deliver the most relevant data required by the users. Web crawling, indexing and searching are different processes that are used for the purpose and the order remains the same. The web crawler which is also known as the web spider works by scanning all the visible links. The web crawler, working as an automated web browser, examines all the pages and takes a decision on the indexing of the pages.

Words found inside the pages are extracted from the description and allocated appropriate meta tags. Meta tags are also taken from contents the webpage itself to establish its relevance. Data from the sites is collected, indexed and stored to be retrieved when it’s needed.

Companies such as Google store all or part of the source web page, while AltaVista stores every page word for word. The information stored and indexed is known as the cache, it allows for instant updating and keeps the searching filtered with ease. An important factor for a successful search engine is its ability to provide active and useable information with minimal to no linkrot. The cache also saves an archive of a removed source that can later be access by the user after the site is updated.

Search engine users normally input a keyword or key phrase into the search field. The engine will search for their particular keyword and key phrase on the World Wide Web. The search engine index will provide an organized list of results with the best matched web pages. A short summary of each webpage describing the contents is provided along with the list.

The goal of major search engines is to supply the most relevant results. Not all sites with the requested keywords are relevant to the search. The search engines have used their spiders and indexing to filter out useless information. They generate their own system for analyzing a website for content.

Page rank is latest addition in the techniques used by search engines to sort out various web pages and their contents. Page rank decides the relevance of a particular page by studying the correlation between its meta tags, descriptions, keywords used and the content of that webpage. The search engines rank those sites high that have association with high ranked web pages. The page rank is essential for any web page or site as it determines its probability of featuring at the top of any particular search.