A PGP key is much longer. There is a "public" and a "private" key. Key lengths are typically between 1024 and 2048 bits. When transmitting a single message to a group, PGP uses a symmetric key for the actual message, then encrypts a separate copy of the symmetric key with the public key of every intended recipient. The sender "signs" the message with his/her "private" key to that others can authenticate the signature with the sender's public key.
I'm too familiar with PGP because it was the underlying security mechanism used by one of my former employers.
Thanks.