[Christians Only] Understanding Genesis 3:15

"And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel." I'm having trouble understanding this whole verse completely. I know that this is the first prophecy of the Messiah and that the messiah is "her seed". What I do not understand is who the woman is? Why is God putting enmity between the woman and Satan? Some help on this would be appreciated