What is Lamb Mutton Yarling?

History of Lamb goes back at least during the times of Genghis Khan. The armies of Genghis Khan, would butcher, lamb. goat, horses. The meat was cut up in to small cubes and threaded on the swords, cooked on wood charcoal. These were just called kebabs. When Babur invaded India, he realized that Hindus did not eat beef. Babur was a Moslem and he did not eat Pork, so the Lamb, Goat and Chicken became the mainstay of Moghlai Cuisine. Sheep was readily available in Northern India, goat was used when sheep was not available. Even when lamb meat is used in India, normally it is mutton. However, in United States, the goat meat is seldom available. So, I have elected to emphasize on lamb. In United States sheep meat is classified by USDA as follow:

Lamb: Less than one year old
Yearling: 1 to two years old
Mutton: Over two years old.

Even in the lamb there are special ratings for 'Dakota Lamb' for leanness and 'Spring lamb' (Born between March and October)
What they sell in most of the grocery stores is 'Lamb' and NOT 'Mutton'. It is legal to sell 'Mutton', but there is very limited demand, so you have to look at specialty stores.

In India, Lamb is basically cut up like either stew meat or ground up.
Stew meat
Lamb Curry
Boti Kebab
Lamb Vindaloo
Lamb Rogan Josh
Ground meat
Lamb Kofta
Lamb Keema
Seekh Kebab
Shami Kebab