The difference between services and factories

angularsnippet

                var myApp = angular.module('myApp', []);

                //service style, probably the simplest one
                myApp.service('helloWorldFromService', function() {
                    this.sayHello = function() {
                        return "Hello, World!"
                    };
                });

                //factory style, more involved but more sophisticated
                myApp.factory('helloWorldFromFactory', function() {
                    return {
                        sayHello: function() {
                            return "Hello, World!"
                        }
                    };
                });

                //provider style, full blown, configurable version
                myApp.provider('helloWorld', function() {
                    // In the provider function, you cannot inject any
                    // service or factory. This can only be done at the
                    // "$get" method.

                    this.name = 'Default';

                    this.$get = function() {
                        var name = this.name;
                        return {
                            sayHello: function() {
                                return "Hello, " + name + "!"
                            }
                        }
                    };

                    this.setName = function(name) {
                        this.name = name;
                    };
                });

                //hey, we can configure a provider!
                myApp.config(function(helloWorldProvider){
                    helloWorldProvider.setName('World');
                });


                function MyCtrl($scope, helloWorld, helloWorldFromFactory, helloWorldFromService) {

                    $scope.hellos = [
                        helloWorld.sayHello(),
                        helloWorldFromFactory.sayHello(),
                        helloWorldFromService.sayHello()];
                }​