RusAlex: legacy, mostly. Community release their own fast-turnaround versions on MELPA.
in fact, getting MELPA (or marmalade) set up is one of the first things you should do.
then you can install things by typing `M-x package-install RET package-name`
(I even have a little function that will lazily load the package, installing if missing) https://github.com/fommil/dotfiles/blob/master/.emacs.d/init.el#L108