Google PageRank: What Do We Know About It?

Everybody is using it, but (almost) nobody really knows how it works. Google PageRank is probably one of the most important algorithms ever developed for the Web. PageRank, only one of hundreds of factors used by Google to determine best search results, helps to keep our search clean and efficient. But how is it actually done? How does Google PageRank work, which factors do have an impact on it and which don’t? And what do we really know about PageRank?