Update 2016-08-19: Comments from my high school graphics teacher :)
See you in space, Commander!
My high school graphics teacher, Master Alan Ceen's, reply:
Git is software for version control of files to help a person or a group of people do, publish and keep track of their work.1 One of the best things about Git is that it is free, open source software. This means that it will always be available regardless of whether a company still exists.
GitHub is a website that provides a good user interface for Git software. It is used by companies like Google — https://github.com/google — Facebook — https://github.com/facebook — and Apple — https://github.com/apple. One of the people2 who created GitHub wrote a parable that helps us see how it works. One of, if not the best, thing about GitHub is it makes it easy for anybody to use Git!
You can easily create a website for free using GitHub and work on it alone or with other people (who have your permission), and publish it on yourusername.github.io or download it to your own computer or transfer it to other servers for editing, publishing or backup.3
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