What is version control?

The problem version control solves

Imagine you're writing an essay. You make a change, then another, then another. Halfway through the fifth revision you realize the third version was actually the best. Can you get it back?

For a single essay you might just copy essay_v1.txt, essay_v2.txt, essay_final.txt, essay_final_FINAL.txt until you cry. For a million-line codebase with dozens of people editing at once, that approach explodes.

Version control is the discipline — and the tooling — of tracking every change to a project so that:

• Every historical state is recoverable.
• Multiple people can work in parallel without clobbering each other.
• You can experiment on a "branch" without breaking the main version.
• You have a story — why each change was made, not just what changed.

Why Git won

There are many version control systems (Subversion, Mercurial, Perforce), but Git has become the de facto standard for software. A few reasons:

1. Distributed. Every clone of a Git repo is a full copy of the entire history. You don't need a network connection to commit or view history.
2. Fast. Git is brutally efficient at computing diffs and merging branches.
3. Branching is cheap. Making a new branch costs almost nothing, which unlocks a style of working where you make a branch for every change.
4. GitHub. A company called GitHub built a social layer on top of Git — pull requests, code review, issues, Actions — and it became the town square of open source.

The three-line mental model

Almost everything you'll do in Git boils down to three verbs:

git add <files>          # stage changes you want to save
git commit -m "message"  # save them as a snapshot
git push                 # send your snapshots to the shared repo

That's the whole core loop. Everything else — branches, merges, rebases, stashes — is a variation on that theme.

A taste of what's next

In the next lessons you'll:

• Make your first commit.
• Open your first pull request.
• Review a PR that Devin opened for you.
• By the end of this module, you'll merge a PR into a real repo and have the commit in your history forever.

AI Tutor tip: if any of this feels fuzzy, open the tutor panel on the right and ask "walk me through what happens when I run git commit" or "what's the difference between git pull and git fetch?".