Communications protocol - Definition from the Hotspot Shield Glossary

Communications Protocols are required for the transportation of messages between computer devices and are an integral part of telecommunications.

A communication protocol defines rules and guidelines for digital messages, and can describe semantics, syntax and synchronization. Without communications protocols, networks couldn’t exist and there are a wide range of protocols available that serve various purposes. In order to communicate with each other, devices have to agree on the aspects of communication - What physical means will data be transferred over? How will both device be able to understand the data? These aspects are defined by communications protocols. Examples of Communications Protocols include UDP (User Datagram Protocol), HTTP (Hypertext Transfer Protocol), POP3 (Post Office Protocol) and FTP (File Transfer Protocol).