Search engine are divided into two main categories:
- Crawler based search engines
- Human editor based directories
Here is a little discussion on that-
Crawler based Search engine:
Crawler based search engines are made up with 3 important components-
- Search Engine Software
Web crawler: A program developed to scan the web pages based on some key factors- keywords, page title, content, anchor texts and also follow links to or from other pages. Once a webpage is crawled, it sent all information to database.
Index program starts, just after Crawling. The index contains a copy of each web pages scanned by Crawler. Any changes in the web pages, update the information indexed. If WebPages are not indexed, the page can never be seen in the search result page (SERP).
Search Engine Software looks for entire indexed pages and sorts all relevant pages, matches with the search terms, rank relevant pages based on how it is programmed for ranking and then deliver the list which it found most relevant.
Ranking Algorithm consider mainly two essential factors-
Off page factor– Inlinks, outlinks, quality links, link popularity, Anchor Text etc.
(These terms also need a long discussion, hopefully in my next blogs) 🙂
Human Editor based Directory:
Here human editors index any site manually in the directory. Webmasters first provide a brief description regarding the site and request to submit their site in the directory. If Editors feel, the site is relevant and has fresh, rich content, only then they index the site into the directory.
photo credit: http://www.SEOcertification.org