What is the significance of Genesis 3 verse 15?

This verse is known as the protevangelium, meaning "The First Gospel."

It predicts continuing hostility between Satan and the woman who represents all mankind and between Satan's seed (his agents) and her Seed (the Messiah).

The woman's Seed would crush the Devil's head, this means a mortal wound spelling utter defeat. This happened at Calvary when the Savior decisively triumphed over the Devil.

Satan, in turn, would bruise the Messiah's heel. The heel wound here speaks of suffering and even of physical death, but not of ultimate defeat.

The significance of this is - this is the beginning of the story of redemption.