In secret-key cryptography, also referred to as symmetric cryptography, the same key is used for both encryption and decryption. In public-key cryptography, each user has a public key and a private key . The public key is made public while the private key remains secret.
Encryption is performed with the public key while decryption is done with the private key.
RSA stands for Rivest, Shamir, and Adleman, the inventors of the RSA cryptosystem. Elliptic curve cryptography has been gaining in popularity recently.