What $httpProvider.interceptors.push does

Question

i am new in angular when reading this article https://www.c-sharpcorner.com/UploadFile/ff2f08/token-based-authentication-using-Asp-Net-web-api-in-angularj/

 

i found few line of code which is not clear to me. those lines are

 

.config(['$httpProvider', function ($httpProvider) {

        $httpProvider.interceptors.push(function ($q, $rootScope, $window, $location) {

            return {
                request: function (config) {

                    return config;
                },
                requestError: function (rejection) {

                    return $q.reject(rejection);
                },
                response: function (response) {
                    if (response.status == "401") {
                        $location.path('/login');
                    }
                    //the same response/modified/or a new one need to be returned.
                    return response;
                },
                responseError: function (rejection) {

                    if (rejection.status == "401") {
                        $location.path('/login');
                    }
                    return $q.reject(rejection);
                }
            };
        });

 please some one help me to understand the above few lines of code and their objective.