Want to learn more about the magic & math behind PGP?
Good. This page includes several links to resources that can help you get started. First, here are a couple of short videos explaining how Public Key Cryptography and PGP work in general:
The math behind Public Key Cryptography is actually not that comples to grasp (but of course it is complex to do!). You can read about it here: http://en.wikipedia.org/wiki/Public-key_cryptography and about the specific design of PGP here: http://en.wikipedia.org/wiki/Pretty_Good_Privacy. The following video explains, in high level, the mathematical aspects of Public Key Cryptography:
Finally, the following video is a tutorial on how to practically use PGP to send encrypted messages. It is a bit hard to follow, but it has historic imporance: it was uploaded to Vimeo by an anonymous user ("anon108") explaining how journalists can use PGP and GnuPG to protect their sources. It was later revealed that "anon108" is in fact Edward Snowden, the NSA whistleblower, who uploaded this video to explain to journalist Glenn Greenwald, with which he was in contact, how to use PGP:
