GitHub is a shared
filing cabinet with a
time machine,
used by programmers
all over the world.
It doesn't just keep the latest version of a file. It keeps every change, from day one until today. Want to go back to any day? You can.
In short: a cloud drive tracks what things look like now. GitHub tracks how they got that way.
Think of it as save files in a video game.
Every time you finish a small chunk of work, you save, and you write one line: "here's what I changed." Saves never disappear, and you can load any of them. About 80% of GitHub's vocabulary makes sense through this one picture.
Working alone, these five steps are enough. The "many people" part starts now.
This is where GitHub earns its keep. Hundreds of strangers can edit the same thing without chaos because of one rule: nobody touches the main line directly.
In short: the main line belongs to everyone. To touch it, you hand in a note and someone signs off. That rule is the whole secret of why it stays tidy.
Come back here when you meet a word you don't know. No memorizing.
A branch is which lines of work exist; a worktree is the desk you lay one out on. Why a second desk beats copying, and when you need one.
A Raspberry Pi for total beginners: credit-card size, costs about $50, and it's slow but can stay on forever, watching over one small daily job.
Same thing on the outside, rearranged on the inside, like re-planning a kitchen's paths without touching the menu. Why it matters and how to do it safely.
A printed black-and-white square that tells a camera "which number, how far, which way": how it differs from a QR code, and why it refuses to guess.