The index

Git has three trees, not two. The working tree is your files. HEAD is the last commit. Between them sits the index — a full tree of its own, holding what the next commit will contain.

Almost every everyday command is a movement between two of these three. `git add` copies from the working tree into the index. `git commit` turns the index into a commit. `git restore` copies backwards. Once you can name which two trees a command touches, git stops being surprising.

`git status` is a report on the two gaps: staged changes are index against HEAD, unstaged changes are working tree against index.