What's the difference between "baby lamb" and "lamb"? Fact #1: A lamb is a baby sheep.

Fact #2: I was watching a cooking show today, and one of the ingredients available was referred to as "baby lamb".

I'm a bit confused as to what "baby lamb" is. I don't think there are "degrees" of "baby-ness"; the sheep is either a baby (a lamb) or it's not. I considered another definition of "baby", as in "baby vegetables", where the item is just smaller than normal. But the pieces of lamb that were indicated didn't look especially small. They just looked like normal meat.

So... What differentiates normal lamb from "baby lamb"? I'm stumped.
According to Britannica:


  The meat of sheep 6 to 10 weeks old is usually sold as baby lamb, and
  spring lamb is from sheep of five to six months.