Their are many Search Engines How they are working that are listed below :
Google
* Gets directory results from DMOZ.
* Furnishes primary search results to Alexa, Netscape, Dogpile, AOL and Go.com.
Yahoo
* Gets paid results from Yahoo Search Marketing.
* Furnishes primary search results to Alta Vista, Alltheweb and Dogpile.
MSN Live and MSN
* Provides paid listings via MSN AdCenter to Microsoft sites.
* Furnishes Dogpile with primary results.
Lycos
* Gets directory listings from DMOZ.
* Gets paid results from Google.
* Gets primary results from Ask.com.
Alta Vista
* Gets directory listings from DMOZ.
* Gets paid results from Yahoo Search Marketing.
* Gets primary results from Yahoo.
Netscape
* Gets directory listings from DMOZ.
* Gets paid and primary results from Google.
Ask
* Gets paid results from Google.
* Furnishes primary results to Lycos, Dogpile and Hotbot.
* Furnishes secondary search results to Snap.com.
HotBot
* Gets directory listings from DMOZ.
* Gets paid results from Google.
* Gets primary search results from Ask.com.
Dogpile
* Gets paid results from Yahoo.
* Gets primary search results from LookSmart, MSN, Yahoo, Google, and Ask.
Alexa
* Gets directory results from DMOZ.
* Gets paid and primary results from Google.
AllTheWeb
* Gets paid results from Yahoo Search Marketing.
* Gets primary search results from Yahoo.
These are all major Search Engines and Their process, The Search ratio in these searcg engines are most, Every webmaster should consider these search engines process when he is doing Search Engine Optimization.