A branch is a parallel copy of your repository. Work on it without touching the main branch, and when it's done you bring it back in. It's the whole reason collaboration is possible: anyone can experiment freely, knowing the main line stays safe.
About 2 min of reading
I wanted to add a login page and nearly edited the live site directly, then remembered branches exist. Let me split main into a parallel copy, work on it, and bring the work back home so main never sees half-finished code.
Start from a clean main with one commit. On this branch the project has just its first version. I am about to leave main untouched and do my experiment somewhere else, so I make sure main has a real commit to build a branch from.
Before you run it, say out loud what it will print. Then open the answer.
Split main into a parallel copy with git switch -c. The new flag creates the branch and moves me onto it in one step. My working copy now shows exactly main, because the branch starts from the same commit, the live site has not changed a single line.
Before you run it, say out loud what it will print. Then open the answer.
Make my feature change here, on the branch, nowhere near main. Because I am on feature/login, this commit lands on the feature branch only. The main branch still has exactly one commit and its own history, untouched.
Before you run it, say out loud what it will print. Then open the answer.
git branch lists every branch I have, and the one with an asterisk is the one I am standing on. This is the check I do before I forget which copy I am working in. feature/login has the asterisk, main has just one commit.
Before you run it, say out loud what it will print. Then open the answer.
Bring the work back home. Switch back to main first, then merge the feature branch in. Git copies my new commit onto main, so main now has the login page and the whole feature history.
Before you run it, say out loud what it will print. Then open the answer.
The feature branch has done its job. Delete it to keep things tidy, main now has everything it shipped, so the branch is only clutter.
Before you run it, say out loud what it will print. Then open the answer.
Before you write anything, put these lines back in the right order. Click a line to move it up one step. This support step is easier than writing code from scratch, and it is here to make the last example stick.
The main branch is the working version of the project. Always do your experimentation on a separate branch, so a mistake mid-way never leaves main broken.
Different people can have their own branches at the same time. Each works alone, then their work is joined back in later. That's how a team can move fast without colliding.
You: "I want to build a login page without breaking the live site."
git switch -c feature/loginmain: the live site
feature/login: your new work, kept separateWhile you build on feature/login, the live site keeps working exactly as before. Nothing you do on the branch can affect it until you deliberately merge. That separation is worth a lot when the code you're writing breaks something.
git switch feature/login
git branchgit switch moves you to another branch. The files on your screen change instantly to match. git branch lists every branch you have, and the one with an asterisk is the one you're currently on.
Switching branches never loses work, it just points you at a different snapshot. Go back to main whenever the feature is finished and ready to ship.
git switch main
git merge feature/loginWhen the feature works and looks good, switch back to main and merge. Git copies your new work onto the main branch. After that, main has the login page, and the feature branch has done its job, it can be removed to keep things tidy.
Each one is defined here on this site. Open the entry for the full definition and the other words it points at.