The pagerank was first introduced "officially" in a paper by the founders of Google. This was on January 29, 1998. Read here the initial paper Since then, this revolutionized the way of the workings of SE, as everybody knows. But in essence, the algorithm itself is not that difficult to understand. Another more recent paper gives an overview of the possible configurations that your website can have to increase in PageRank. And so, yes, the algorithm itself is well known. There are however some tweaks to it that are not generally known, and give Google the "extra edge". Back in 1998, this was however basically the start of their business. Remember also that they became and still are big, because of the Adsense stuff. And that's only loosly related to PR...
The pagerank was first introduced by Google in 1998. It was made public via the Google toolbar in 2000.
PageRank was developed at Stanford University by Larry Page (hence the name Page-Rank) and later Sergey Brin as part of a research project about a new kind of search engine. The project started in 1995 and led to a functional prototype, named Google, in 1998. Shortly after, Page and Brin founded Google Inc., the company behind the Google search engine. While just one of many factors which determine the ranking of Google search results, PageRank continues to provide the basis for all of Google's web search tools.