When to create a new controller in rails

Question

I\'m wondering when you know that you need to create a controller in a rails application.

For example, I\'m going through the tutorial in Agile Web Development with

Answer 1

A controller can be used to create pages with no boundary to a model. An example for that might be an legal notice or sth. like that. Static stuff,...

A Controller controlls data. In most cases these data comes from the Model but this isnt necassary wheater its the most common combination.