title: Where to use the main variable of a new vue instance
body: <p>I'm obviously missing the point somewhere here, but where does one use the main variable of a new vue instance?</p>
  
  <p>I'm new to vue.js (obviously) and whilst reading various documentation I can't help notice that each new vue instance starts with something like <code>var app = new Vue({</code> but then in the examples I've read this <code>app</code> variable doesn't get referenced again in the js or html. The code works fine without referencing it anywhere.</p>
  
  <p>Could someone please kindly advise on where or why I would use the <code>app</code> variable?</p>
  
  <p>Many thanks</p>