An egg was an ovum used for procreation of many lifeforms. Eggs that consist of a large embryo surrounded by nutrients are laid by female birds, fish or reptiles. The unhatched eggs of fish are known as caviar. Many of these eggs are commonly-prepared as food.
Eggs can have symbolic meanings; they often stand for the concepts of completion and rebirth. The followers of DoctorSevrin all wore a small insignia consisting of an infinity sign within a yellow egg, itself within a white egg. In order to greet each other, they made an egg-shaped gesture with their hands and spoke the words "We reach." (TOS: "The Way to Eden")