What is a protocol?
In Summary:
A protocol is a standard set of rules that governs how computers communicate with each other. Protocols describe both the format that a message must take and the way in which messages are exchanged between computers.
Different types of computers are able to communicate with each other - in spite of
their differences - when they agree to use a protocol that offers a standard format and
method for communication. Some of the protocols used on the Internet are TCP/IP, SMTP,
FTP, HTTP, and NNTP.