(probably dumb) question about use of pgp and gpg

["Robert P. Goldman" <goldman@htc.honeywell.com>]

I feel a certain obligation to start using some crypto stuff, but I'm
a little bewildered by the fact that there are two alternatives ---
pgp and gpg --- available.

gpg seems to be the preferable choice for me:

1.  it is less restricted in licensing use, so I don't have to ask
    myself every time I use it whether a particular message is
    commercial or not;

2.  the pgp command-line I got for linux seems much less
    well-documented and easy to use than the gpg that came with my red
    hat.

Question:  is gpg fully compatible with pgp so that I could use gpg
happily?  Or is it incompatible, in which case adopting it means that
there'll be nobody I can exchange encrypted messages with?  I have a
document that is supposed to explain how to use gpg as a pgp
replacement, but it's not very clear and does not seem up-to-date.

Thanks!
R

P.S.  If there's a suitable RTF* type response to this question,
please feel free to point me to some source of information that's
readily available and accept my apologies.