Either you're a spammer or a newbie. I'll give you the benefit of the doubt and suggest you start here to learn about SEO and link development. (In particular, chapter 7 gives a good answer to your question).
For traffic in the end. The best way to get traffic is by having your site appear in top in first page of google search result if someone do searching using your keyword. So you need to build quality backlinks to high PR sites. The more quality backlinks to other high PR sites, the more chance your site PR itself will also increase. If your site PR is higher than among all your competitors in a spesific keyword, then for that keyword your site will appear in most top of first page of google search result of the keyword. 42% of searchers click No. 1 site in first page means if there are monthly 1,000,000 unique people search your keyword, then you will get 420,000 monthly unique visitors.