1. The Mental Model

Git has three local areas and one remote:

Working Directory  →  Staging Area (Index)  →  Local Repo  →  Remote Repo
   (your files)         (git add)              (git commit)    (git push)

Area	What lives here
Working Directory	Files you're actively editing
Staging Area	Snapshot of changes you've selected for the next commit
Local Repository	Full project history (.git/ folder)
Remote Repository	Shared copy on GitHub/GitLab/Bitbucket

Key insight: git add does NOT commit. It stages. You choose exactly what goes into each commit.

Every commit is a snapshot, not a diff. Git stores complete file states, then uses delta compression internally.

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