What does #! mean in ui.router?

Question

I am using the Angular ui.router to navigate through my application. Usually, the url should look like this:

http://localhost:8001/#/start

But in my case, it looks like this:

http://localhost:8001/#!/start

What does it mean?

I also recognized that if I am calling an URL from this site which is different from my start page, I always get redirected as the URL seems to be invalid.

mainApp.config(['$stateProvider', '$urlRouterProvider', function ($stateProvider, $urlRouterProvider) {
'use strict';
$urlRouterProvider.otherwise('start');
$stateProvider
    .state('start', {
        url: '/start',
        templateUrl: 'views/start.html'
    })
    .state('registration-activate', {
        url: '/registration/activate/{activationKey}',
        templateUrl: 'views/registration-activation.html'
    })
    ;
    }]);

Whenever I try to call localhost:8001/#/registration/activate/xyz I get redirected to the start page.

Answer 1

Okay guys, thanks for your explanations. I resolved my problem that I can't call a URL from a link simply by adding this to my configuration:

$locationProvider.hashPrefix('');