RubyGems is a package management application for Ruby that is used to quickly and easily distribute Ruby/Rails applications and libraries. If you are planning on doing any development in Ruby, this is a must have. RubyGems is for Ruby as apt-get and yum are to Linux operating systems. This article will show you various ways to install it depending on what Linux distribution you are using. 详细参考：http://heatware.net/ruby-rails/how-to-install-rubygems-linux-ubuntu-10/