Learning Emacs Lisp
People who have been using Emacs for a while often develop the desire to learn Emacs Lisp, so they can customize Emacs more extensively, develop extra packages and create the ultimate editing experience, uniquely tailored to their needs & preferences.
You can discover many other Emacs-related blogs on Planet Emacslife.
Emacs distributions are basically extensive Emacs configs aiming to improve the default user experience. Various distros have different goals, focus of philosophy, so choose accordingly.