Carbon & Cocoa- and the difference between them

As a year old Mac user (meaning, I've been using the Mac for a year, I personally am not a year old) one thing has always had me a bit miffed

What's the difference between Cocoa and Carbon?

My understanding is that is has something to do with the appearance of an app- and how it was created.

Just a little curious, that's all!

Cheers