The chicken is the domestic bird that produces the eggs most commonly sold as chicken eggs.
Domestic chickens are descended primarily from the red junglefowl of South and Southeast Asia. They were domesticated thousands of years ago and are now kept worldwide for both meat and eggs. Specialized laying breeds can produce many eggs over a year, although output depends on genetics, age, nutrition, light, and health.
The eggs sold in ordinary grocery markets are usually chicken eggs because chickens are efficient, adaptable, and comparatively easy to keep in large numbers. Duck, turkey, and guineafowl eggs are also edible, but they are less common in mainstream retail markets and are usually labeled by bird species.
Chicken eggs vary in shell color, including white, brown, blue, and greenish shades, but shell color does not reliably indicate nutritional quality.