Cryptographic Protocol is one of the Cryptography?

In the time before 1976, majority of the people were using secret key to hide a message, this secret is only known by the parties involved in transferring the message. This method is called Symmetric Algorithm. Since then different types of method has introduce to hide a message by using a public key and a secret key. This method is called Asymmetric Algorithm. These two algorithms are the main branches of Cryptography. Beside this, there is also another branch called Cryptographic Protocol, to be frank, I am not really sure what this have to do with the cryptography algorithm?