Clarify the route url and area meaning

Start of the document says don't worry if you don't know MVC but this section was not well documented at all.

Added comments to clarify what these magic route fields mean. I followed along with this to add the tutorial into an existing project and it took me a while to figure out what was what.

Ideally I would like to rename the module to something like ExampleCompany.HelloWorld or somesuch so that it doesn't just have "HelloWorld" throughout the code everywhere when they regularly mean different things, however I'm working on a project at the moment and don't have time to update the code + downloadable project. 

I think these simple comments will hopefully help newbie developers for now.