Susie, no worries your not Highjacking anything :-)
Having a pr ranking is something that google gives you when your
blog gains in size and you are doing the right stuff. LOL not sure
what everything is the right stuff but, they only update like 4
times a year.
But, when you get a pr ranking you can use that to show sponsors
or people wanting to work with you, and you can raise your paid
post price or whatever cause it shows that you rank in searches and
such. But, I don't know a ton about it. Just know it is good to
you can check your site there for free :-) and they might
explain it better then me.