It would be wise to learn about version control. It doesn't necessarily have to be GIT although it's pretty popular these days.
It also doesn't have to be GitHub. There are other GIT options out there.
GitHub is not a revision control system GitHub is a git repository. Git is a revision control system and can be used without GitHub. This is a common misconception. GitLab is another git repository.
There are many revision control systems available. Some of the more common open source ones are cvs, subversion (svn), mercurial (Hg), git and fossil. There are also numerous commercial revision control systems. See...
There are also many source code hosting sites offering support for various revision control systems including GitHub, GitLab, SourceForge, CloudForge, Bitbucket, and GNU Savannah amongst others. See...
Some revision control systems can also store binary data, though not as efficiently. This means even game assets such as music, images and models, as well as the source code can be controlled.
In any large project a version control system should be considered essential.