Google

Google is fast becoming the most richest company in the world (Walmart holds that position) it is currently valued at making roughly $69 Billion a year from its advertising revenue. Originally the search engine software was written by two students at Stanford University by Larry Page and Sergey Brin. They wanted to create software that indexes the internet. Larry Page's name is given to the phrase "PageRank" as it was his ability to write software that recognised 'keywords' and their relevance in finding a relavent site - so in "Search Engine Optimisation" your content and keywords dominate.

Originally in 1991 the only software available was "Archie" and "Gopher" . Yahoo! came into existence when two students( Jerry Yang and David Filo) created a search engine software in January 1994. However Yahoo! became cumbersome in it's loading as advertising was introduced to its search page - and so in 1996  Google took over and the rest is history - many search engines have appeared (Altovista, AskJeaves, Excite, Lycos, etc.) But only one has dominated due to its simpliticty of being one of the best web crawlers.

So when you search on Google's servers - you're not searching the internet as such (that is impossible) only searching the index of Google which scans and then stores cached pages of its monthly scan of the internet. However - be careful when writing your website and make sure you have all the links correct otherwise Google will see missing links. Basically Google reads only words and links URLs.