Search engines allow us to find specific information. Users notify the search engine of new pages. They maintain an index of the contents of every page they find. They periodically check out old connections to make sure they still exist. A recent survey showed that the best search engines have indexed less than half of the over 3 billion web pages on the web.
All search engines have their own prioritizing or weighting schemes.
The first word in a search is ranked more important than later word. Keywords in tags may still be used by some search engines. How many other sites link to this site or page. Some allow sites to pay for a higher ranking It is important to use more than one search engine. Search Engines may be grouped according to their functions or where they search.