What does it mean that Christ was not creted but 'begotten'?

Check out this quote:

We don't use the words begetting or begotten much in modern English, but everyone still knows what they mean. To beget is to become the father of: to create is to make. And the difference is this. When you beget, you beget something of the same kind as yourself. A man begets human babies, a beaver begets little beavers and a bird begets eggs which turn into little birds. But when you make, you make something of a different kind from yourself. A bird makes a nest, a beaver builds a dam, a man makes a wireless set—or he may make something more like himself than a wireless set: say, a statue. If he is a clever enough carver he may make a statue which is very like a man indeed. But, of course, it is not a real man; it only looks like one. It cannot breathe or think. It is not alive.

Now that is the first thing to get clear. What God begets is God; just as what man begets is man. What God creates is not God, just as what man creates is not man.