Ruby on Rails topics and roadmap (demo)
Install Ruby on Rails on Fedora Linux
gem: is a Ruby package (Rails is just a big gem)
bundler: A tool for installing dependencies. It allows you to switch between versions of Ruby (to run different versions of an app, for example). It will look for the Gemfile where all the versions are defined.
To start the app: ruby server (or ruby s) (rails s)
rails-i18n - The Ruby I18n (shorthand for internationalization) gem which is shipped with Ruby on Rails (starting from Rails 2.2) provides an easy-to-use and extensible framework for translating your application to a single custom language other than English or for providing multi-language support in your application.