What is Curriculum?

It's a big question. My first answer is that it's that big binder the people in Regina created for us to follow as we teach a variety of subjects.

As I reflect on my journey of trying to come to a deeper understanding of what is curriculum, I have narrowed it down to one simple statement: Curriculum is the definition of what is taught. So that can mean many things, including the prov. documents previously mentioned. As well it can include the overt, hidden and nulled curriculum introduced to us in class.
The 'simple' statement brings to mind 2 major questions, to which I have few answers.
Does curriculum have anything to do with what is learned?
Who truly makes the decisions of what is taught, not what should be taught, but what actually is taught?