Что такое вложенные маршруты (nested routes)?

{
  path: '/user/:id',
  component: UserLayout,
  children: [
    { path: '', component: UserHome },
    { path: 'profile', component: UserProfile },
    { path: 'posts', component: UserPosts },
  ],
}

<!-- UserLayout.vue -->
<template>
  <section>
    <h1>User {{ $route.params.id }}</h1>
    <nav>
      <router-link :to="`/user/${$route.params.id}/profile`">Profile</router-link>
    </nav>
    <router-view />
  </section>
</template>