Plaintext: original data before encryption
Cyphertext: data after applying encryption algorithms
Key: a string that is used to encrypt or decrypt data
Public key: the key of the asymmetric key pair that is shared with the public
Private key: the key of the asymmetric key pair that is kept by the receiver
Symmetric cryptography uses the same key to encrypt and decrypt data, hence the name 'symmetric', meaning the same on both sides.
Asymmetric cryptography generates a public-private key pair where the public key is used for senders to encrypt messages and the private key is used for the receivers to decrypt messages, hence the name 'asymmetric', meaning different on the two sides.