The person spoken of in Genesis 3:15 is called the seed of the woman - and not of the man - which can agree with no other than the Messiah, who was to be born of a virgin, which was afterwards more clearly revealed by Isaiah 7:14 ("Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel"). This was fulfilled in Jesus, who was truly the seed of the woman and of her only, being made of a woman and not begotten by man. He was conceived in the womb of the virgin by the power of the Holy Spirit.
The work he was to do deserves consideration and proves the person spoken of to be the Messiah, which was to bruise the serpent’s head - that is, to destroy Satan and all his works, set aside all his craft and cunning, crush all his machinations and designs, and overturn his whole empire. Now, this is frequently spoken of in the Old Testament, as the Messiah’s work. In some places, a peculiar reference seems to point to this original prophecy, as in Psalm 110:6, which belongs to the Messiah and thus prophesied of him. "He shall wound the heads over many countries" may also be rendered as "he shall wound the head," that is, him that is the head, or ruler, over a large country, which is no other than Satan, the god and prince of this world. In Habakkuk 3:13 it is said, "You went out for the salvation of your people, for the salvation of your anointed. You crushed the head of the house of the wicked, laying him bare from thigh to neck."
From this first prophecy, we learn that the Messiah was to be incarnate, born of a woman and not begotten by man. He was to suffer and die. Also, he was to destroy Satan and his works, which Jesus has done.
Adapted from The Prophecies Respecting the Messiah, Chapter II, by John Gill.