The three areas

$ git status

All three areas agree: the working directory, the stage and the last commit hold the same snapshot. "Working tree clean".

$ edit index.html "<h1>Hello, friend!</h1>"
$ edit style.css "h1 { color: tomato }"

We edit two files. Only the working directory changes — the stage and the repository still hold the old versions.

$ git status

git status compares the areas for you: two files are modified but "not staged for commit".

$ git diff

Plain git diff shows working directory vs. staging area: what you changed but have not staged yet.

$ git add index.html

We stage just index.html. Watch it move onto the stage — style.css stays behind in the working directory.

$ git diff --staged

git diff --staged shows staging area vs. last commit: exactly what the next commit will contain.

$ git restore style.css

We decide the tomato colour was a bad idea. git restore <file> overwrites the working copy with the staged version. Careful: those edits are gone, not saved anywhere.

$ git commit -m "Friendlier greeting"

Click. The commit is made from the stage, not from your folder. All three areas agree again.

$ echo "remember the footer" > todo.txt
$ git add todo.txt
$ git restore --staged todo.txt

Staged something by accident? git restore --staged <file> takes it off the stage but keeps your file. todo.txt is back to untracked.

$ git status

Untracked files are ones git has never been told about. They are never committed until you git add them.