In main.js generated with vue-cli tool

import Vue from 'vue'
import App from './App'
import router from './router'

Vue.config.productionTip = false

/* eslint-disable no-new */
new Vue({
  el: '#app',
  router,
  template: '<App/>',
  components: { App }
})

[template: '<App/>']What does this sentence mean?
Does it mean using the app.vue template? But I haven’t seen such usage in vue!
There are only:
1 template:'#xxx' Get based on id
2 template:'<xx>...<xx>' Use it directly
Is there any related one? What about the documentation? Thanks