Dotfiles are all the hidden settings and configuration files you have on your Unix system.
I wrote a bit on how you can set up and start customizing your shell from scratch as well as how to set up a dotfiles folder and share it on GitHub here.
My own dotfiles can be found here. They are always in a state of flux. But I am learning and adapting things as I go.
bluz71 - Interesting vim setup.
caarlos0 - Made antibody.
wangsongiam - Interesting Hammerspoon and Zsh config.
Keith - Vim, Zsh, Tmux, and macOS.
bresilla - Neat Linux look.
Jess Frazelle - Docker/Linux.
Roma Volosatovs - Private NixOps network infrastructure.
yqrashawn - Made Goku.
Gleb Skibitsky - Uses Goku/Karabiner.