How is the ion-nav done in ionic 4?

I would like to know how to implement it in my project since in the documentation they do not give almost information of that component

Hi

The Routing & Navigation concept has changed from Ionic 3 to 4.
If you use for example Ionic with Angular, Ionic is using directly the Angular-Router:
https://angular.io/guide/router

Ionic-Docs:

I mean the component, friend