'billboard' is one implementation method that can used to display them in a 3D game, but the interface/design/concept is very common in 2D games too (going back many years).
Yeah, I was referring to the "technical term" for rendering them in 3D. As an interface/design concept, the term billboard is not accurate. It wasn't clear whether the OP wanted to know how to render it, or how it should be called in a design doc., an in-game tutorial, etc