I'm not saying it's an "index" to clarify what "staging area" means, I'm saying "index" is a synonym for "staging area" so if he runs into the word "index" somewhere, he knows it's just a different word for the same concept. For Christ's sake, there's nothing magic about the words, they're just names for something. If you didn't know what a dog was, and I said "a dog (aka a canine) is a domesticated animal related to a wolf", I'm not expecting the word "canine" to add anything to the explanation, I'm just throwing it in there in case you run into someone else who says "canine" instead of "dog", just so you know that in both cases they're referring to the same type of thing.

In any case, a staging area only makes sense in the context of trying to create a commit, and I think I did usefully define what a commit is. Maybe that part should have come first.