What is config() method in AngularJs

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8" />
  <title>What is config() method in AngularJs</title>
  <script src="https://code.angularjs.org/1.4.9/angular.js"></script>
  <script src="https://code.angularjs.org/1.4.10/angular-route.js"></script>

  <script>
    var app = angular.module('app', ['ngRoute']);
    app.config(['$routeProvider', '$locationProvider', function($routeProvider, $locationProvider) {
      //This is route provider.
      $routeProvider.when('/', {
        controller: "myCtrl"
      });

      //This is location Provider.
      $locationProvider.html5Mode({
        enabled: true,
        requireBase: true
      });
    }]);

    app.controller('myCtrl', ['$scope', function($scope) {
      $scope.user = "This is Anil";

    }]);
  </script>
</head>

<body data-ng-app="app">
  <div ng-view></div>
  <div>
    <form>
      <input type="text" required>
      <input type="submit">
    </form>
  </div>
</body>

</html>