The initial setup:

<div ng-app="app" ng-controller="AppCtrl">
  {{ title }}
</div>

var app = angular.module("app",[]);

app.factory("game", function () {
  return {
    title: "StarCraft"
  };
});

app.controller("AppCtrl", function ($scope, game) {
  $scope.title = game.title;
});

Factories are a common paradigm in Angular that allow you to configure a function that returns an object which can be then injected into controllers. Here, the game parameter to the controller is injected and matched to the game factory, which returns an object with a title attribute.

But what is a factory?

To demonstrate the factory can be refactored into the $provide service:

var app = angular.module("app",[]);

app.config(function ($provide) {
  $provide.factory("game", function () {
    return {
      title: "StarCraft"
    };
  });
});

app.controller("AppCtrl", function ($scope, game) {
  $scope.title = game.title;
});

The $provide service sets up the injector for any factories defined on it. The above example functions identically to the initial setup.

$provide.factory is shorthand for $provide.provider, which sets up a more generic provider which returns objects that have $get functions:

var app = angular.module("app",[]);

app.config(function ($provide) {
  $provide.provider("game", function () {
    return {
      $get: function () {
        return {
          title: "StarCraft"
        };
      }
    };
  });
});

app.controller("AppCtrl", function ($scope, game) {
  $scope.title = game.title;
});

This also functions identically to the initial setup. ‘factory’ is simply an alias for this longhand method of declaring a provider which returns an object with a $get method.

var app = angular.module("app",[]);

app.provider("game", function () {
  var type;
  return {
    setType: function (value) {
      type = value;
    },
    $get: function () {
      return {
        title: type + "Craft"
      };
    }
  };
});

app.config(function (gameProvider) {
  gameProvider.setType("War");
});

app.controller("AppCtrl", function ($scope, game) {
  $scope.title = game.title;
});