PGP encrypted email - basic questions

Hello all-

I'm trying to get started with PGP and there are some concepts I am
having trouble with.

I understand that a recipient of a PGP signed/encrypted message will
have to get my public key to decrypt said message. What I don't
understand is how this is carried out in a seemingly automatic fashion
for many of the email messages I receive, e.g. postings from mailing
lists, in which I see the 'BEGIN PGP SIGNED.. ' and the signature at
the end. I didn't decrypt these messages, and I have no idea how they
got decrypted.

When I encrypt a message and send it to myself, the message I see is
decidedly not decrypted. I did notice this header..

OpenPGP: id=5847D5CF;
url=http://random.sks.keyserver.penguin.de:11371/pks/lookup?op=get&search=0x5847D5CF

in the outgoing encrypted test message I sent, which leads me to
suspect that it might have something to do with this process, but
still, my message is not decrypted.

How does this work?
Dave
--
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A human being should be able to change a diaper, plan an invasion,
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problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects. -Heinlein