Gems can be used to extend or modify functionality in Ruby applications. Commonly they’re used to distribute reusable functionality that is shared with other Rubyists for use in their applications and libraries. Some gems provide command line utilities to help automate tasks and speed up your work.
The RubyGems software allows you to easily download, install and use Ruby software packages on your system. The software package is called a
gem and contains a packaged Ruby application or library.