Protocol is most often used when talking about the rules of government or official agencies. It is derived from the French and refers to the correct rules of etiquette for diplomats.
The term protocol is used in many areas besides diplomatic ones. School marching bands or college admissions offices follow protocols, and doctors use them to treat patients with specific conditions. In tech circles, a protocol is a set of standards that programmers follow so that their work can be decoded by other computers. The p in the http of a web address is short for protocol. Without this type of protocol, you would not be able to read this page.