Pagerank is a concept developed by Larry Page one of the founders of Google. Essentially Larry was trying to find a way to categorise all of the university papers and doctrines into some sort of importance. He used the concept that if a paper referenced another paper it would mean that the paper that had been referenced was important. The more papers that referenced that paper the more important and credible it was. In the same way the papers that these papers referenced gained importance in the same way. And so on. Thus if a paper that was very important made reference to another paper this would be worth more in the scale of things. Larry essentially needed to crunch some serious numbers and that is where his partner Sergey Brin comes in. Sergey was the mathmatician who worked out an algorithm to crunch this problem down and make some sense of it.
Thus they then replaced these doctrines with the entire web and references with links and crunched the entire web universe down. They then stored this data and displayed it as you see it today.
Thus Pagerank (Larry Pagerank) is all about the number of websites that link to your website. Aswell as a ranking of how those websites that link to you are. I.e. depending on the pagerank of the websites that link to you this will determine your pagerank.
How to use this info:
1. Get more websites to link to you that have high pagerank.
2. Get more links (references) to your website.
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