Routing is one of the primary aspects of the MVC framework which makes MVC what it is. While that is possibly over-simplifying, the routing framework is where the MVC philosophy of "convention over configuration" is readily apparent.
Routing also represents one of the more potentially confounding aspects of MVC. Once we move beyond the basics, as our applications become more complex, it generally becomes necessary to customize our routes beyond the simple flexible default MVC route. If you are new to MVC, first review the basics of MVC Routing, then take a quick tour of route customization: