Digital signature is the electronic equivalent of a handwritten signature
Encryption is the process of converting information or data into a code, especially to prevent unauthorized access.
Private key (secret key) refers to a key used for symmetric encryption; also, the member of a public key pair that must be kept secret.
Public key encryption is a form of encryption that uses two keys. A public key, which everyone knows, and a private key, which only you know.
Secure Sockets Layer is a protocol which creates a secure connection between a client and the server over which to send information.