Navigation in Ionic does not work using normal routing like you might have done in some of the client side web frameworks, especially when compared to browser based navigation. It uses the terminology of pages which I find is more generalised and correctly named as compared Ionic version 1's states. This approach is quite similar to navigation in a native mobile application.
Pages are pushed and poped from the navigation controller a class defined whose subclass available in Ionic is ion-nav. The logic here is equivalent to that of a stack. The purpose of ion-nav is to work with the navigation stack.
To define a nav bar in an ionic app:
https://gist.github.com/d2d8eda3a2b903db2fdbdfdee1d873bc
Inside the typescript file associated to above HTML code, we will have access to Navigation Controller.
https://gist.github.com/c41ee05b929410aa708fab137739eae8
Thus, we can access NavController and it's properties such as push and pop to navigate to a different page or back to the previous page.
Note: Deeplinking is available in Ionic with URLs but that is altogether a different topic.