Question - What are nested routes? 
          
        
        Answer - 
        
Generally, the app is composed of nested components which are nested multiple levels deep. The segments of a URL corresponds to a certain structure of these nested components. To render components into the nested outlet, you need to use the children option in VueRouter constructor config.
Let's take a user app composed of profile and posts nested components with respective routes. You can also define a default route configuration when there is no matching nested route.
const router = new VueRouter({
  routes: [
    { path: '/user/:id', component: User,
      children: [
        {
          // UserProfile will be rendered inside User's  when /user/:id/profile is matched
          path: 'profile',
          component: UserProfile
        },
        {
          // UserPosts will be rendered inside User's  when /user/:id/posts is matched
          path: 'posts',
          component: UserPosts
        },
          // UserHome will be rendered inside User's  when /user/:id is matched
        {  path: '',
           component: UserHome },
      ]
    }
  ]
})