PR Links are incoming links from sites with Page Rank. The higher the PR, the better benefit to you, on the surface. It also will depend on how many links are leaving that site, on how much PR will be transfered to you. It also used to mean that a site with PR was listed in Google's Cache, however today it doesn't mean its listed in the main index, so checking to see what pages are cached is as important.

Some will argue its important, others will disagree. The main criteria today, so many will say, is if the site linking to you is of importance, if the link is natural. Paid Links are frowned upon by Google, as they prefer links that are natural, meaning it makes sense for site A to link to you, not because of money. It is supposed to improve relevancy of the link.

hth
Ian :morning: