What is a "Box", Web Programming Concept?

Yesterday, I was in a conversation with someone regarding Amazon Web Services (AWS) and web servers, at large. The person kept using the term "box" to refer to something on the server side, perhaps something to do with deployment, containers, or the environment in which something is running. I have never heard this term before; however, the conversation did not permit my asking what a box is.

Is this a common enough term that someone can provide me with a definition? Or, is the such a contextual use that it has no meaning beyond its context within the conversation?

I have done a bit of research and am unable to find the term used elsewhere.