in the *nix world programs are configured in two different ways, via arguments in the terminal or text based configuration files. programs which have many options like your shell, window managers, or even text editors are configured on a per-user basis with files in your home directory ~. in unix like operating systems any file or directory that starts with a period or full stop character is considered hidden, and in a default view will not be displayed. thus the name dotfiles. it's been said of every console user:
you are your dotfiles
i manage mine with gnu stow, a free, portable, lightweight symlink farm manager. it allows me to keep a versioned directory of all my config files that are virtually linked into place.
Read: managing your dotfiles »
atom is a "hackable text editor for the 21st century" created by the team at github. it's designed to be customizable, but also usable without needing to edit a config file.
this quote really sums it up perfectly:
Read: atom editor linux install »
git is a distributed revision control and source code management (SCM) system with an emphasis on speed. git was designed by linus torvalds, of linux fame, for managing the development of the kernel. every git working directory is a fully fledged repository, complete with revision tracking abilities independent of a network or centralized server. git is 100% open-source, freeware, and distributed under the GNU general public license v2.