What is the difference between a public and private key?

A public key is a cryptographically generated string of numbers and letters that is used to authenticate and encrypt information. The public key is shared and typically used to encrypt messages sent to a particular recipient. A private key, on the other hand, is a unique, cryptographically generated string of numbers and letters that must remain confidential and is only known by the recipient. The private key is used to decrypt information that has been encrypted with the public key.