[recursive]

The official documentation for `git add` refers to "the index". I'm not seeing any reference to multiple indexes. I've been using git for years, and I've never heard of it. I read a book about it. But parts of it are definitely still mysterious to me. Anyway, where can I find any evidence of these 4 indexes?

[rendall]

Sorry, category error. I was using index to refer to the category of which index is a member. Maybe areas is better. These are the 4 ... things...:

working directory - this is the project directory in the OS file structure

index - a.k.a the staging area

repository - in the .git directory

stash - a kind of scratch pad or clipboard for the developer

Understanding these different areas and how and why to move data into each is essential to understanding git

[Quenty]

While you are correct, this is not what I was referring to.

To be exactly clear, there are actually 4 staging areas within what you referenced as the index. This is indeed a detail most people do not worry about.