I am learning how to write a System Requirements Specifications, and most of templates I have seen talk of a Context Diagram.
What exactly is a Context Diagram?
A Context diagram is used to depict the "environment" in which the system under design has to operate. It is usually drawn as a bubble for the system and the entities that interact with the system (both human and computers) around it, connected to the system with lines.
Sometimes, the context diagram also shows (in keywords) what kind of interaction there is between the system and an external entity (for example, that a Customer might 'place an order').