Encryption keys are secret sets of letters and numbers used to encrypt or decrypt data.
In symmetric encryption, the same key is used for encryption and decryption.
In asymmetric encryption (with a public key), a key pair is generated:
Public key (public) — a public code used to encrypt data. Knowing the public key does not allow you to know the private key.
Private key (private) — a code that is available only to its owner. Allows you to decrypt data encrypted with a public key.
Public key encryption enables a digital signature mechanism to be implemented.