Glossary Term Definition: 

In the context of computing, a protocol is a special set of rules that enable communication between two computers.

A useful physical analogy is a traffic light: on green lights, cars pass through intersections; on red lights, cars are not permitted to pass through an intersection. The rules represented by traffic lights can be considered traffic protocols; the rules for computer-related tasks such as data transfer are computing protocols.

HTTP is one example of a computing protocol.