The document discusses Ruby gems and plugins. It provides an overview of what gems are, how the RubyGems package manager works to distribute and install gems, and some of the benefits of using gems. It then profiles several popular gems, describing their functionality and how they can be used. These include gems for authentication, pagination, file attachments, testing, scheduling tasks, and more. Lastly, it lists the authors of some "über-gems" and provides brief biographies.