A protected/private character string which is applied to authenticate an identity, which gives secure authentication and secure SSL authentication, sometimes with digital signatures and digital certificates like 128 bit SSL digital certificates. Passwords are for a user's online security or authorization security. Working together are certs and secure email with ssl certificates, all terms related to online security.
Similar to "protocol" in human communication which involves a previously agreed upon set of rules for communicating in diplomatic settings. On the Internet, a protocol is an agreed upon method for sending and receiving information.
A key that is kept secret from the public in asymmetric encryption. Each of the two parties involved in the communication have a pair of keys each (one public, one private). They exchange public keys but neither gives the other their private key.
A key that can be obtained from a designated authority for asymmetric encryption. The key is a value that can be used to encrypt (code) or decrypt (decode) data for a single transaction. In asymmetric communication, both a private key and a publicly available key are required to exchange secure messages.