title: What is _events and what is it used for?
body: <p>Searching <a href="http://backbonejs.org/docs/backbone.html#section-17" rel="nofollow">backbone</a> I see it is used 12 times and always attached to <code>this</code> inside of Backbone.Events.</p>
  
  <p>Is it simply a property of Backbone.Events?  If so why does it have the underscore prefix?</p>
  
  <p>What is it used for?</p>
  
  <pre><code>on: function(name, callback, context) {
        if (!(eventsApi(this, 'on', name, [callback, context]) &amp;&amp; callback)) return this;
        this._events || (this._events = {});
        var list = this._events[name] || (this._events[name] = []);
        list.push({callback: callback, context: context, ctx: context || this});
        return this;
      },
  </code></pre>