Not a stupid question as you're right
I mostly use "com" to reference my component but yeah by giving the mapping a reference name of "component" ColdFusion will look to use the directory path you've specified there to find your components.
Only thing to keep in mind is this technique is application-specific. Mappings in the CFAdmin are global to every application running within ColdFusion, these ones will only work for files that are running within the same application - Hope that makes sense.
BTW in your code example you don't need the application.dsn in quote marks or hashes. You're calling a variable so you can simply write it as this
[INDENT][/INDENT]getTypes = siteCFC.getTypes(application.dsn);
Also, "food for thought". You could do this
[INDENT][/INDENT]siteCFC = createObject("component", "components.cfcSite").init(application.dsn);
Where init() is what they call a constructor (Google it ). You load the application.dsn value into the CFC on start up and it stores it internal. That way you don't need to reference it everytime you call one of its functions as the CFC can just use the value it was previously given.
It's also worth thinking about just using the function calls when you need them rather than saving the results in a variable. More OOP