What is the difference between sperm and egg?

Sperm is a male gamete and an egg is a female gamete. In plants when the male gametophyte undergoes meiosis it produces four sperm cells. When the female gametophyte goes through meiosis it makes one egg cell and three polar bodies. When the process of fertilization occurs in angiosperms (flowering plants) there is double fertilization. Double fertilization is when one sperm fertilizes the egg and another fertilizes a polar body so that in the seed that develops there is the embryo (fertilized egg), and the endosperm (fertilized polar body, nutrition source for embryo).

In animals, eggs are much larger, non-motile, and have a full complement of organelles. They have a larger food store than sperm. Sperm are smaller, flagellated so they can swim, and really only have DNA and mitochondria to power the flagella. Sperm has protein in it's head to dissolve the egg's cell membrane.