Google's "PageRank" Concept Explained

Google has managed to keep ahead of the competition since its launch in 1997 in great part because it revolutionized the way web pages were ranked. Google Search was built on the concept of "PageRank", a web page ranking system that takes into account not only on-site content, but also the popularity of the web page. Using advanced algorithms for link analysis, Google determines the relevance and popularity of a given page for the targeted keywords.
Traditional Ranking
Before the concept of PageRank and link analysis, the only thing that search engines took into consideration was "on-site" material. This meant that, as long as the web page contained the targeted keywords several times, it would rank high on the search results. Meta keywords and meta description tags were used to determine the site's primary keywords. Of course, this method or ranking led to a considerable amount of spamming, as you only had to add words to a web page, whether they were relevant or not, to get it a high ranking.
After PageRank started becoming the primary way in which all major search engines ranked sites, this keyword spamming method became much less useful.
PageRank and Link Analysis
The link analysis method employed in the PageRank concept relies on the exceptionally democratic nature of the World Wide Web and its immense interconnected link structure. The more a page is linked to, the more value it has in the eyes of search engines. In other words, each time another web page links to your web page, it's like they're adding a vote to your page. The more votes you get, the more important you look and the higher your search engine ranking becomes.
But it's not just about how many votes you get. It's also about who votes for you. Votes cast by pages that are themselves highly ranked, are going to carry more weight than votes from pages that are not as popular. Because links are largely given out by third parties that have little vested interest in the success of the site they are linking to, other than how useful they believe the site to be, it is not only much more difficult to obtain and manipulate your PageRank "score", but it's also a much more democratic and accurate way of assessing the value of a given site.

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