ion-nav-view is an angular directive. The code You pasted here are routes that manage templates and the url. They are created with this angular plugin: Angular UI Router
If You want to have the same header on all pages using ion-nav-view is the way to go. If You want to research the directive in the code You need to search for ionNavView (without the dashes).
If you want for example the Rock page have some elements common from the “Music” page You should read about nesting views in the ui-router: UI Router wiki