title: Groups in a Gemfile in Rails 3?
body: <p>In my Gemfile in Rails I have these groups:</p>
  
  <pre><code>group :development, :test do
    gem "capybara"
    gem "database_cleaner"
    gem "spork"
    gem "launchy"
  end
  
  group :bdd do
    gem "cucumber-rails"
    gem "rspec-rails"
  end
  </code></pre>
  
  <p>What does this mean?</p>