Does <ion-nav-view> accepts ng-template only as a page?

Ionic Framework ionic-v3
1

for example, if I want to create an app which can navigate several layers, eg:index->a1->a2, do I need to write it as:

<body ng-app="todo">
<ion-nav-view>
</ion-nav-view>
<script id="a1.html" type="text/ng-template">
    <button href="a2">to a2</button>
   <script id="a2.html" type="text/ng-template">
    to a3
   </script>
</script>
<script id="b1.html" type="text/ng-template">
</script>

which has so many layers of ? can I use normal page (e.g.:separate file a1.html) as one of the navigating page?