EGG! I do not understand why these questions are so... "mysterious".
An egg is an egg, but if you think of it in terms of evolution, over generations some random birds (always laying eggs) eventually gave birth (laid egg) to a bird similar to a chicken, but it is not a "chicken" then that bird eventually laid an egg and out of that egg came a chicken. Eggs stay the same, the bird changes.
Nuff sed.