A persons dotfiles are all the files that begin with a dot (.) in Linux/UNIX. These usually contain personalizations and customizations of a persons work environment. Backing these up -- usually with GIT -- is pretty important to do so that you can easily setup a command-line environment from any machine on the Internet simply by cloning the GIT repository and running a setup command of your own creation.

Frequently a dotfiles setup is combined with a private repo containing private data so that the dotfiles repo can be made public and referred to by others looking to pilfer cool ideas about how to make their own dotfiles better. This is a long-standing Linux tradition. Creating one's own dotfiles is something of a right of passage in the Linux community as demonstrated by the >10,000 dotfiles repos on GitHub/GitLab.