People.get()

When you use parenthesis - the function (in this case People.get()) will get executed straight away and the return value assigned to $scope.people

Since we want to get the list of people straight away, this makes sense right?

$scope.people = `People.get()

The others don't have parenthesis because we don't want to execute the function right there and then. All we want to do is assign the actual function to $scope so that we can call it at a later date.. for example once we've clicked on the remove button.

Hope that clears it up.

I agree with Ben.

$scope.people = PeopleFactory.get();
// this METHOD needs to be invoked by the controller to get the collection from the factory as part of initialization. (Even though the ARRAY is empty).

$scope.people = PeopleFactory.add; // NO parenthesis

$scope.people = PeopleFactory.remove; // NO parenthesis

// These METHODS are only invoked when ng-click="add(person)" or ng-click="remove(person)" events are triggered by clicking on the respective button element

I believe each need to have the parens, I think this was just an oversight in the video.