Original: Bird and reptile eggs consist of a protective eggshell, albumen (egg white), and vitellus (egg yolk), contained within various thin membranes.
Simplified: Most eggs that are eaten by humans, including birds' eggs and turtle's eggs, have a protective, oval eggshell, the albumen (egg white), the vitellus (egg yolk), and various thin membranes, that are layers like skin. Every part of the egg is edible, although the eggshell is usually thrown away.