Comment by 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