title: res.json(), where is it responding?
body: <p>I am new to the routing section and try to understand what's going on with this code , specially with res.json</p>
  
  <pre><code>router.get('/', function(req, res){
    db.find()
    .then(function(todos){
      res.json(todos);
    }
  })
  </code></pre>
  
  <p>I need to know where this res.json is responding, is it to the frontend when they need it or is it for the database part? when we try to find all the info from the database using find() and then converting it into json, where is it going? </p>
  
  <p>and the same for the POST route when we try to create a new Todo with create() we use res.json() again, here we are trying to post info to the server so why are we using res here?</p>