Word
GitHub
GitHub is a website that stores a copy of your project's version history online, so it is not only on your laptop.
Also called: remote, the repo host
Git runs on your machine. GitHub is the place you push a copy to. That copy is what survives a dead laptop, what the computer running your app picks up from, and what lets someone look at your project without you emailing a folder around.
Most of what you do with it is one command meaning "send what I have saved."
The mistake that actually costs people: a settings file with live keys gets added to the project and pushed, and those keys are now somewhere you cannot take them back from. Anything inside a commit is in the copy.