Pretty Good Privacy, or PGP, is a data encryption and decryption program that provides cryptographic privacy and authentication for data communication. It is widely used for securing emails and files, ensuring that only intended recipients can access the information. Developed by Phil Zimmermann in 1991, PGP uses a combination of symmetric-key cryptography and public-key cryptography to protect data. This dual approach allows users to encrypt messages with a unique key while also enabling secure key exchange, making it a cornerstone of modern digital security practices.