A chicken is a generic name referring to domesticated descendants of the jungle fowl of South-East Asia. During the course of history, chickens have spread throughout the world, and evolved into many different forms as a result of domestication. There are many specialist breeds of chickens, but the terms broiler and poussin refer to the more commercial varieties. A broiler is a meat-producing bird grown till 5-8 weeks of age and weighing about 2.5 kilograms. A poussin is a small tender broiler grown to about 3 weeks of age.