A comb is a fleshy growth on top of a chicken's head. In chickens, a healthy comb is usually red.
Colour can vary in other bird species, such as turkeys, and certain breeds, such as silkies, which have blue/black combs While both genders of chickens have combs, the comb is usually much larger on males than hens.
Comb shape can vary greatly, especially with crossbreeding, the most common variation is the single comb.
Rose combs are usually rather flat and close to the bird's head. Sometimes it will form a point and extend further back than the rest of the comb.
Note the Rosecomb is also a breed of chicken. Rosecombs are bantam chickens, and are among those known as true bantams (meaning they are not a miniaturized version of a large fowl. Rosecombs are one of the oldest and most popular bantam breeds in showing, and thus have numerous variations within the breed. As an ornamental chicken, they are subsequently poor egg layers, and not suited for meat production.