Branches are the only part of git that feels like cheating. You can break things in a copy and never once touch the real project.
About 2 min of reading
A branch lets you break things in a copy that shares nothing with your real project. Let me split one off, break it on purpose, and bring it back.
Start from the commit I already made on main, and make sure of it. git branch with no arguments lists every branch I have and marks the current one with an asterisk. Right now main is the only one there.
Before you run it, say out loud what it will print. Then open the answer.
Split off and switch in one move. -b means create, and the name after it is the branch. My folder now shows the same files as before, but any commit from here goes to the new branch, not main.
Before you run it, say out loud what it will print. Then open the answer.
Now break something on purpose. Edit the finished file, stage it, commit it. The change lives entirely on feature-login. main has not moved an inch, the real work is untouched.
Before you run it, say out loud what it will print. Then open the answer.
Confirm the mess is mine and main is clean. git log --oneline shows only my broken commit on this branch. Switch back to main and run the same command, my broken commit is nowhere to be seen.
Before you run it, say out loud what it will print. Then open the answer.
Time to bring the real work back. Merge the branch into main. Git stitches the two histories together on top of main's latest commit. Since I only touched login.py on one side, there is nothing to fight over, the merge just works.
Before you run it, say out loud what it will print. Then open the answer.
There is no magic box of branches. A branch is a small label that points at a commit. main just points at your latest commit on the main line, and feature-login points at the latest commit you made on that branch. Creating or moving a branch only moves the label, the commits already exist.
Two ways eventually join branches:
git merge branch # adds a merge commit, keeps both histories
git rebase branch # replays your commits on top, straight lineFor now merge is the safe default. rebase is a sharpening tool you'll learn in the Advanced lessons, it looks cleaner but rewrites history, so it is not for work you have already shared.
git checkout -b feature-login-b means create a new branch named feature-login and switch to it in one move. Your folder now shows the same files as before, but anything you commit from here goes to the new branch, not the main one. Make a mess? No problem, the real work is safe on main.
git checkout mainI built a whole feature, committed it happily, then tried to push from main and found my work missing. I had simply forgotten to switch back off feature-login. Switching back is the command above. Git moves your working files to match whatever branch you are on, so this also undoes the confusing feeling before it starts.
git checkout main
git merge feature-loginOnce the feature is done and tested, merge it back into main. Git stitches the two histories together. The awkward part happens only when both branches touched the same lines, then git stops and asks you, which is where the next lesson starts.
Each one is defined here on this site. Open the entry for the full definition and the other words it points at.