Is Ruby and Ruby on Rails essential to app development?

Question

I have the Ruby course started on here, and tons of more resources for Ruby and it's framework, Ruby on Rails. I plan on making an app and I need to know if those 2 will help. Thanks!

Answer 1

web app - yes
mobile app - barely

Answer 2

I know twitter uses both but I heard it couldn't handle the large scale of its users so yeah