An egg is a biological structure that contains a developing embryo of a bird, reptile, amphibian, or fish. It provides the embryo with nutrients and protection while it develops. The embryo grows into a new individual of the species.
The egg consists of a yolk, a white (albumen), and a shell. The yolk provides the embryo with nutrients, the albumen provides water and additional nutrients, and the shell protects the embryo.
Eggs are one of the most common forms of reproduction in the animal kingdom. They allow animals to reproduce without the need for the mother to carry the developing embryo inside her body.