Ignoring pictures...

[Onslaught]

Porn has penetration and sex in it. Girls fingering them selfs or sucking off guys and what have you.
Nudes are just tasteful pictures of someone without cloths. That's how I would describe the difference
between the two.
Playboy just has pictures of girls doing things like riding horses or holding a baseball bat with no cloths on.
You know, stuff girls do all the time when we're not around!

But porn has girls taking it and doing the nasty kind of stuff that you want your girlfriend or wife to do.

[Byteme]

Present day Playboy is a shadow of what it once was: trying to keep up with the intertubes has not been kind to it. Still, its far and away light years better tham FHM or Maxim, and is still a good mag for the one or two good articles in it per issue.

And that's in a universe where there are only maybe half a dozen good magazines in current publication.

In the 60's Playboy was the leader in good writing.  Jean Shepherd, P.G. Wodehouse, Norman Mailer, Kurt Vonnegut, Shel Silverstein, Isaac Asimov, Ian Fleming, John Updike, S.J. Perelman, Woody Allen, Bruce McCall, Steve Martin, Harvey Kurtzman, Jules Feiffer, Lenny Bruce, Arnold Roth, and a hundred others (I could name them if I could be bothered to crawl up int he attic and dig out my 60's issues.  I was probably one of the few who had a subscription to Playboy before I was old enough to drive).

Anybody who was anybody was or wanted to be the subject of a Playboy Interview.  An inspired highlight was sending Alex Haley to interview the head of the American Nazi Party, George Lincoln Rockwell.

[Soup DeVille]

What's the difference between nudes and porn?

Do nudes not show any vagina but porn does?

Man, if you have to ask: do your own research.

[93JC]

What's Penthouse like these days? It's been years since I've seen one. Last I heard they'd moved to hardcore, but toned it back down a couple years back.

[Raza]

What's the difference between nudes and porn?

Do nudes not show any vagina but porn does?

Porn is generally a bit more explicit.

[Byteme]

What's the difference between nudes and porn?

Do nudes not show any vagina but porn does?

Playboy would show a nude in a pose in which you might see the vagina. It was just there, the girl's pose didn't draw attention to it.   

Penthouse would have the girl's hands and head positioned in such a manner that the shot came to be known sarcastically in the adult publication industry as the "checking for crabs" shot.