lots of interesting insights and data points about google exist but i want to focus for now on part of an article in wired magazine. 

hal varian, who among other things is google's chief economist, talks about adwords and reveals a bit more about how it works.  everytime someone clicks search on google a silent real time auction takes place to decide who gets one of the 11 sponsored slots on the results page.  one blog described it as 'the world’s biggest, fastest auction, a never-ending, automated, self-service version of Tokyo’s boisterous Tsukiji fish market'

the article also discusses the reasons behind why google gives away its products- its browser, its apps, and most recently the operating system android for mobile phones. 

go and take a read here