RPG stands for "role playing game" so I basically think of it as a story heavy game where you take the "role" of the protagonist. Despite this I wouldn't consider most VNs to be RPGs as they lack the gameplay element of the "playing" part of RPG (picking between choices isn't really enough to count as "gameplay" in my opinion; while I love VNs I find them closer to books than games). I would count the Zelda franchise as an RPG though because despite many titles being puzzle heavy the story is still important and there is a combat element to it. I agree with others that a RPG is easier to recognize than explain.