From wikipedia:

In software, a package management system, also called package manager, is a collection of software tools to automate the process of installing, upgrading, configuring, and removing software packages for a computer’s operating system in a consistent manner

Why is this powerful ?

Suppose I want to install a software package, I need only to execute the following command, and homebrew does everything for you:

Compare that to:

In addition, I could harness the ‘powers’ of the command line interface and automate all of my software installations like so:

What about apps ? Easy! just use cask, an add on to the brew system:

brew tap caskroom/cask
brew install brew-cask
brew cask install dropbox
brew cask install google-chrome
brew cask install firefox

Convinced ? Head down to http://brew.sh/ and get it now ☺