Navigation between pages was straightforward in the early days of the web. One could type a URL in the browser’s address bar to retrieve a precisely identified resource. After all, a URL is used to point to a single, physical resource (a file) on a server. When a page was loaded, we could follow hyperlinks to jump between resources as well as use the browser’s back and forward buttons to move between visited items. The rise of dynamically rendered pages broke this simple navigation paradigm. All of a sudden, the same URL could result in different pages being sent to a browser, depending on the application’s internal state. The back and forward buttons were the first victims of the highly interactive web. Their usage became unpredictable, and many websites are still going as far as discouraging the use of the back and forward navigation buttons (encouraging users to rely on internal navigation links). Single-page web applications didn’t improve the situation, far from it! In modern, AJAX-heavy applications, it is not uncommon to see only a single URL in the browser’s address bar (the one that was used to initially load the application). Subsequent HTTP interactions happen through the XHR object, without affecting the browser’s address bar. In this setup, the back and forward buttons are completely useless, since pressing them would take us to completely different websites, instead of a place within the current application. Bookmarking or copying and pasting a link from the browser’s address bar is not much use either. A bookmarked link will always point to the starting page of an application. But the browser’s back and forward buttons and ability to bookmark URLs are very useful. Users don’t want to give them up while working with single- page web applications! Fortunately, AngularJS is well-equipped to help us handle URLs with the same efficiency as in the good, olden days of the static resources web!
URLs in single-page web applications, from Mastering Web Application
Development with AngularJS, by Pawel Kozlowski & Peter Bacon Darwin