title: Backbone JS Models and Collection URLs
body: <p>If I have a model named "Book" and a collection named "Library" defined as below:</p>
  
  <p>Book</p>
  
  <pre><code>app.Book = Backbone.Model.extend({
      defaults: {
          title: 'No title',
          author: 'Unknown'
      }
  });
  </code></pre>
  
  <p>Library</p>
  
  <pre><code>app.Library = Backbone.Collection.extend({
      model: app.Book,
      url: '/api/books'
  });
  </code></pre>
  
  <p>When I call <code>BookInstance.save()</code> how does it come up with the URL to use? Does it derive it from the collection?</p>
  
  <p>In <code>Backbone.model</code> there are 2 options: <code>url</code> and <code>urlRoot</code>. What is the purpose and difference between these?</p>
  
  <p>In <code>Backbone.collection</code>, there is a single parameter <code>url</code>. Is this always the GET request for the RESTFUL api?</p>