Cryptography is the scientific discipline for the study and development of ciphers, in particular, encryption and decryption algorithms. These cryptographic procedures are the essential components that enable secure communication to take place across networks that are not secure. SSL encryption uses both symmetric and asymmetric keys.
Symmetric (secret) key
Secret key cryptography means that the sender and receiver share the same (symmetric) key, which is used to encrypt and decrypt the data.
The secret key encryption and decryption process is often used to provide privacy for high-volume data transmissions.
Asymmetric (public/private) key
Public/private key cryptography uses an asymmetric algorithm. The private key is known only by its owner and is never disclosed. The corresponding public key can be known by anyone. The public key is derived from the private key, but it cannot be used to deduce the private key. Either key of the pair can be used to encrypt a message, but decryption is only possible with the other key.