Can't access to my namespace in a function

I am doing a school assignement where we have to do a small application which manage a monster by following a pattern but my lesson is very badly explained so I understand nothing, I can't make the difference between public and private, I know what is the difference in Java, Php but not in js.

Here is what it does, when I load the page, it execute run() in monster.modules.app and this should execute showMe() in monster.modules.actions, the problem is I get this TypeError: monster.modules is undefined..

So can you explained me why I can't access to monster in this public or private function ?

And why do I have to put functions into parenthesis ? (function(glob) {

  /**
  * Etape 1.1
  */
  // NAMESPACE : monster
  var monster = monster || {
    modules : {}
  };

  /**
  * Etape 1.2
  */
  monster.modules.actions = (function() {
    /**
    * Etape 1.2.1
    */
    var name;
    var life;
    var money;
    var awake;

    return {
      /**
      * Etape 1.2.2
      */
      showMe : function() {
        alert('Monster ' + this.name + ' : {life : ' + this.life + ', money : ' + this.money + ', awake : ' + this.awake + ' }');
      },

      /**
      * Etape 1.2.3
      */
      init : function(name, life, money, awake) {
        this.name = name;
        this.life = life;
        this.money = money;
        this.awake = awake;
      }
    };

  })();

  /**
  * Etape 1.3
  */
  monster.modules.app = (function(){
    /**
    * Etape 1.3.1
    */
    var show = document.getElementById('b6');

    return {
      /**
      * Etape 1.3.2
      */
      run : (function(){
        console.log('run');
        show.onclick = (function(){
          monster.modules.actions.showMe();
        });

      })
    };
  })();

  /**
  * Etape 1.3.4
  */
  window.onload = (function(){
    monster.modules.app.run();
  });




}) (window);