Google Page Rank?

I stil cannot understand how this Google PR is determined because until now mine never changed at all as far sa PPP is concerned! I am still showing as N/A there while those newly created blogs have already registered a high PR4! Probably, my blog has no traffic at all or whatever determines google ranking is confusing me. I don't know what else to do! Will someone explain it to me, please? Sorry, just venting and confused.