SC.routes manages the browser location. You can change the hash part of the current location. The following code
SC.routes.set('location', 'notes/edit/4');
will change the location to http://domain.tld/my_app#notes/edit/4. Adding routes will register a handler that will be called whenever the location changes and matches the route:
SC.routes.add(':controller/:action/:id', MyApp, MyApp.route);
You can pass additional parameters in the location hash that will be relayed to the route handler:
SC.routes.set('location', 'notes/show/4?format=xml&language=fr');
The syntax for the location hash is described in the location property documentation, and the syntax for adding handlers is described in the add method documentation.
Browsers keep track of the locations in their history, so when the user presses the 'back' or 'forward' button, the location is changed, SC.route catches it and calls your handler. Except for Internet Explorer versions 7 and earlier, which do not modify the history stack when the location hash changes.
SC.routes also supports HTML5 history, which uses a '/' instead of a '#' in the URLs, so that all your website's URLs are consistent.