Site Routing lets you handle what happens when a user enters a specific address in your domain. Site Routing can use URL's that are not directly connected to a page file.
A good example is if you have an info page whose address is "mydomain.com/info" and you also want anyone who enters "mydomain.com/about" to get to your info page, you can use Site Routing to do this.
Routing also lets you redirect users using with a HTML redirect code and permanent redirect code to either a page on your site, a path in your domain or URL.