Page Rank is based on links between your site and other sites, in fact specifically between web pages, since it is links between individual pages rather than complete websites that interests Google. That is because Google lists individual pages and not domains. There is a formula that Google uses to determine the value of each link to your site, which is based on the PageRank of the web page providing the link and also the number of other links leaving that page.
You can see the page Rank in the Google PageRank bar on the Google Toolbar - it is the green bar that shows a numerical value of 0 to 10 when you hover your cursor over it. This value is logarithmic, which means that if it takes 10 links to reach PR 1, then it takes a lot more to reach 2. If Google uses a logarithmic factor of 8, as it might do (nobody knows), then it will take 8 links to your site to get to PR 1, 64 to reach PR 2, 512 to PR 3 and so on. This is very basic, since, as I have stated, it also depends on the PR of the page providing the link and the number of other links leaving that page.
Here are the top 4 reasons that in my opinion help most to generate traffic and make you money:
1. The higher your Google PageRank, then the higher Google is likely to list you in the search engine results pages. Google take the view than the more other websites link to yours, then the more relevant your web page must be to the topic in hand, otherwise they wouldn't link to you. In fact, the links are to specific pages in your site, not to the site as a whole, which is why it is called 'Page Rank' and not Site Rank.
2. The higher the Page Rank, then the more relevant other people will consider any particular page on your website to be. They will feel more confident that if they visit your site they will have their questions answered and find the information they are looking for.
3. A high Page Rank shows that you have a high number of links on the pages of other websites. There is then the possibility of others clicking on these links to get to your website.
4. The higher your Page Rank, then the more people will want you to link to their website. That means that they too will be likely to visit your site. They will also offer you a reciprocal link if you want one, and that too will provide you with more exposure online.
They are all different URLs that will lead somebody using them to your domain. However, search engine spiders see them all as different URLs, and if you use different ways to write your home page URL, then they will all be listed separately, and all be given a different Page Rank. Thus, the page rank for any one of them will be weaker than your page would have been if you had used only the one way to express it. Get into the habit of expressing your domain in only one way.
There are other ways in which poor use of your website URLs and also injudicious linking policies, can harm your Page Rank, but the main point that should keep in mind is that the your page rank applies to each page individually, and you get a share of the Google PageRank of the page that provides you with the link. If that page has a PR of zero, then you get nothing.
In giving my reasons for page rank being important in building traffic, I should stress that it is not one of my more important ways. However, Google takes notice of your PageRank, otherwise why would it bother giving you a Page Rank in the first place. For that reason alone it is well worth building up as many links back to your webpages as possible, not just for the traffic, but also to keep your website in the public eye.
It is the Home Page that is highest listed on most search engines, and also the page is given the highest PageRank, so if you can persuade others to link to your home page in return for a link from a page internal to your site, then that would be a good deal, and is what you should be trying for.
Don't ask me though, because I would a link back from your highest Page Ranked page!
Page Rank is an important property of your website, and for more information on internal and external linking strategy check out Pete's website Improved Search Engine Rank where you will find many other SEO tips.