What good does it do my website if my PageRank is high?
Does it mean I get more traffic and is so how?

PageRank is not directly connected with traffic (other than possibly spider traffic).

It's a general indication of the number and quality of links to your website from other people's websites. Search engines use this information to help them decide how popular your content is.

If the PR is high, then you are more likely to rank well, which can result in more traffic and customers.

That's the simplified answer. The real answer is a lot more complicated, since there have been many people buying PR and doing other things that make Google not trust it as much as it used to, and it has responded by changing how it deals with PR.

Most SEO's will tell you to not focus too much on PR, as it doesn't have the same effect it used to. Having said that, for Joe Average the non-spammer who is very careful about getting on-topic links, it's probably still a useful indicator.

Just remember, PR doesn't bring in customers and rankings; links and content do. PR is simply one method of measuring links. As such, you should spend more time on links and content themselves.

PR Mania used to be a really big thing, and if you read older articles on SEO, you will find ones that positively gush over PR as if it was the key to riches. That really wasn't true back then, and is certainly not true today.

Ian