It means different things to different people, and different airports.
In the strict sense, Dublinpilot is 100% right. You must make a
positive two-way contact, and obtain a confirmation of the permission with the planned destination and also with the alternate.
In the UK, this is easy. Just phone them. They speak English! It's a good idea anyway; they might be shut or whatever.
In Europe generally, it gets more tricky, partly due to language and partly due to often inaccurate published contact info. I've been refused landing a few times, in one case from short final on an IFR flight, and that was at Padova (Italy) who had a fax from me (which they denied having) and I was unable to phone them (no reply). Sometimes (Corsica comes to mind) they hang up when they hear a foreign language on the phone. Sometimes there simply isn't an English speaker on the phone despite it being an airport with Customs (Pamplona, Spain, as well as various Italian places) and several faxes and emails send over the preceeding days are not answered. The vast majority of published email addresses, even those on airport websites, are duff. Many fax numbers are duff too
It can be done, and there is a kind of a process one can follow, but it can take a while to sort it out. And it has to be done.
In the UK, a lot of "PPR" is the result of a planning permission deal with the local council.
Abroad, a lot of "PPR" is ostensibly to enable the airport to control apron capacity, but usually you get around it by "paying more" (going via a handling agent).
BTW - I gather that Duxford has recently re-examined their way of dealing with PPR, for the better (due to the word getting about, resulting in a loss of visitors).
As I said on the other thread, I think a lot of PPR is illegal because a public airport has to be open.