It is using the modern browser features to do the trick.
read the official angular docs.
https://angular.io/docs/ts/latest/guide/router.html#!#browser-url-styles
Appendix: LocationStrategy and browser URL styles
When the router navigates to a new component view, it updates the browser's location and history with a URL for that view. This is a strictly local URL. The browser shouldn't send this URL to the server and should not reload the page.
Modern HTML 5 browsers support history.pushState, a technique that changes a browser's location and history without triggering a server page request. The router can compose a "natural" URL that is indistinguishable from one that would otherwise require a page load.
Here's the Crisis Center URL in this "HTML 5 pushState" style: