RubyStack is a tool that makes it easy to deploy Ruby on Rails applications. It provides a self-contained, relocatable environment with all necessary components like Ruby, Rails, MySQL, and Apache bundled together. The RubyStack installer uses BitRock InstallBuilder to create installers with a graphical user interface that work across operating systems. RubyStack provides unattended installation options and tools like Capistrano for automating deployment. Under the hood, RubyStack bundles optimized versions of all required libraries and components to provide a complete development and deployment solution for Ruby on Rails.