Page Rank
It is a number from 1 to 10 that google assigns to each URL on the web, and URLs that have PR 10 are the best. Obviously, that PR 9 is less better than 10, but it's still great.
The problem is that the PR is not made public anymore (it's stopped being public many years ago, 6-7 years, maybe more, I don't remember) and only google knows what PR each URL has. Those guys on Fiverr can't know shit, they are just mentioning the word PR because 1) they are too lazy to update their gig's descriptions, or 2) they hope to impress newbies like you into buying their gig