PGP is encryption software that scrambles files and e-mail messages before sending them over the Internet. If someone does intercept your encrypted message, either in transit or while stored on a mail server, all they will find is a long passage of gibberish called ciphertext . Not all encryption is created equal. Just as you can buy flimsy or robust locks to protect your valuables, you can use different strengths of encryption to secure sensitive data.
Encryption strength is determined by the length and complexity of the key.
Unlike the passwords for servers or e-mail accounts, which only block someone's entry, an encryption key actually encodes and decodes the contents of messages and folders by applying a complex coding algorithm, or cipher, to the data. The more complex the code and the more intricate the process of encrypting and decrypting data, the more difficult and time-consuming it is for a snoop to decipher the code and view your message. This means that to encrypt or decrypt information each party must already possess the necessary key. This presents two problems. First, you can't exchange information with anyone who does not already have your key.