Glossary is missing 'HEAD' and 'Staging area' #32

Context

Git prints both words at people constantly — "HEAD detached at abc123", "Changes not staged for commit" — and never explains either. They are two of the most alarming-looking things a beginner meets.

What to change

Files: data/glossary.json

Requirements:

• Add one object for HEAD and one for Staging area
• For HEAD, say plainly that "detached HEAD" is not damage
• For the staging area, explain what git add actually does
• Mention the alternative name "index" for the staging area

Acceptance criteria

• Both terms appear on the glossary page
• The HEAD entry would reassure somebody who just saw the detached-HEAD message
• The JSON still parses

How to verify locally

python3 -m http.server 8000

Then open http://localhost:8000.

Difficulty

Beginner.

New here? Comment /claim on this issue and a bot will assign it to you. Then read CONTRIBUTING.md.

Stuck at any point? Comment here saying what you have tried and where it stopped working — that is not an admission of failure, it is how we find out the instructions were unclear. You can also come to a PR Debug Clinic (Oct 12 or Oct 21).