Lamb, hogget, and mutton are the meat of domestic sheep. The meat of a sheep in its first year is lamb; that of a juvenile sheep older than one year is hogget; and the meat of an adult sheep is mutton. Lamb is a sheep less than a year old, typically slaughtered between the ages of 4 and 12 months. And the mutton has a much stronger flavor.
Color is a good indicator of age. The lighter the color, the younger the meat. Baby lamb should be pale pink. Regular lamb is pinkish-red. When selecting lamb, take into consideration the tenderness of the cut so you will know how to cook it. Tender cuts require fast cooking over moderate to high heat, while less tender cuts are better for braising and stews.