Protocols are rules and procedures for communicating. When several computers are networked, the rules and technical procedures governing their communication and interaction are called protocols.
How Protocols Work
The entire technical operation by which data is transmitted over the network has to be broken down into discrete, systematic steps. At each step, certain actions take place that cannot take place at any other step. Each step includes its own rules and procedures, or protocol. These protocol steps must be carried out in an order that is the same on every computer in the network. In the sending computer, these steps must be executed from the top down. In the receiving computer, these steps must be carried out from the bottom up.