The PageRank is a value that indicates how important your webpage is, this is partly determined by the link popularity, this is the number of links you get from other sites. It is often abbreviated to PR and is a (secret) calculation done by Google. There are a lot of theories and thoughts on the internet about how important a high page rank is, and Google itself usually does not comment, so it remains guesswork. Generally speaking, a higher PR allows for a better position in the search results (so with a PR of 1 you come on page 4 of the results, but with a PR of 6 maybe on the 1st page).