Working of Search Engine

       Search engine follow these steps in order to perform ranking of site.

• CRAWLING
• INDEXING
• PROCESSING
• CALCULATING RELEVANCY
• RETRIEVING RESULTS

CRAWLING -

  In this crawlers or spiders fetch the webpages linked to a site. Crawlers or Spiders are basically   softwares of search engines. e.g googlebot is crawler of Google. Slurp for Yahoo, Bingbot for Bing, Scooter for Altavista.

INDEXING-
It is the process of creating the index for the all fetched webpages and storing them into the database.

PROCESSING-
When we request search on engine, the search engine processes it. It (search engine) compares the search string in the search request with the pages in the database which are indexed.

CALCULTING RELEVANCY-
Since there are more than one pages of search available. So search engine calculates the relevancy of each of the pages in its index to the search string. These indexes are stored in giant database.

RETRIEVING RESULTS-

The is last step. Search engine retrieves best matched results and showing them in browser.

IMPORTANT-

Search engines often update their relevancy algorithms. When you see changes in your rankings it is because of changes in their relevancy algorithms and user can do nothing in it.
The basic principle of all operation of the all search engines are same but due to minor differences in their relevancy algorithms there are major changes in their results relevancy.