Ruby is a breakthrough in allowing web development as one can make use of Gems to fill in functionalities. This allows one to build a web app in matter of days which would usually take months to develop. Gems are highly modular and perform a specific function, which makes integrating them into new applications extremely easy. Out of the multitudes of gems created by the Ruby community at large for use, we pick fifteen which, in our opinion, are the recommend ones that should be present in every web application.

Reference: https://codebrahma.com/best-gems-for-ruby-on-rails-web-applications/