Search Engine:

• Search Engine is an application that is used to search for information on the Internet according to a specified criterion.
• Without search engines, finding the desired information from the colossus Internet would be painstaking and cumbersome task.
• In other words, the search engine searches the Internet for the information you want and displays it on your computer screen, all within a few seconds.
• Therefore, the task that would have taken hours to be completed by you if you do it manually can be now done in seconds by the search engine.
• Some popular search engines are Google, Yahoo, MSN, AltaVista, Look Smart and Netscape.

Algorithm-Based Ranking System:

Understanding how crawling, indexing, and ranking works is helpful to SEO practitioners, as it helps them determine what actions to take to meet their goals. This primarily covers the way Google and Bing operate. The search engines must execute multiple tasks very well to provide relevant search results. Put simplistically, you can think of these as:

• Crawling and indexing billions of documents (pages and files) on the Web (note that they ignore pages that they consider to be “insignificant,” perhaps because they are perceived as adding no new value or are not referenced at all on the Web).

• Responding to user queries by providing lists of relevant pages.

  Crawling and Indexing:

  • The web has link structure which serves to bind all the pages that were made public during linking with other pages.
  • The search engine automated robots also known as crawlers or spiders have capability to reach billions of into connected documents.
  • Once the engine finds these pages, its next job is to parse the code and store selected pieces in the form of array on hard drives. The retrieval is done when it is called through query.

Retrieval and Ranking:

• After crawling and indexing the search engine returns a list of relevant pages on the web to satisfy user requirement.

• Two things are involved in this process:

  • Only related result should be returned which is asked in users query.
  • Rank the result as per importance taking into account the trust and authority associated with the site.

• Relevance:

  It is degree of matches found in any document returned by search or the amount of data related to the users query intention. Relevance is the first step if the web pages are not relevant to the search query as the search engine does not consider them for search results.

• Importance or popularity:

  It refers to the relative importance which is measured through citation. It can also be considered as out of one work referencing another. If a given document matches with users query the citation increases with number of other document that references it. Popularity and relevance cannot be determined manually, to achieve these search engines which have algorithms and several mathematical equations.