Root element missing? [problem resurfaced]

[Crimson Wizard]

What does file version control mean?

It is the system that keeps records of the history of project changes. It stores all the stages of your work in a kind of database, called "repository". There are also web services that host such repositories, even for free (with certain restrictions).
It may take some time to learn using one, but I believe it is worth it.
You may look out for SVN or Git, for example.