In networking, a protocol is a set of rules and conventions that govern the communication between devices. The data that is being transmitted between devices is often referred to as the “payload” or “application data.” The protocol defines how this data is packaged, or formatted, and how it is transmitted over the network. It also defines the rules for error checking and correction, and for establishing and maintaining connections between devices. In short, a protocol is a set of rules that allow different devices to communicate with each other effectively and efficiently, and the application data is the actual information that is being transmitted using those rules.