In the "Create Components" section of AngularJS's homepage, there is this example:

controller: function($scope, $element) {
  var panes = $scope.panes = [];
  $scope.select = function(pane) {
    angular.forEach(panes, function(pane) {
      pane.selected = false;
    });
    pane.selected = true;
  }
  this.addPane = function(pane) {
    if (panes.length == 0) $scope.select(pane);
    panes.push(pane);
  }
}

Notice how the select method is added to $scope, but the addPane method is added to this. If I change it to $scope.addPane, the code breaks.

The documentation says that there in fact is a difference, but it doesn't mention what the difference is:

  
Previous versions of Angular (pre 1.0 RC) allowed you to use this interchangeably with the $scope method, but this is no longer the case. Inside of methods defined on the scope this and $scope are interchangeable (angular sets this to $scope), but not otherwise inside your controller constructor.

How does this and $scope work in AngularJS controllers?