God created man in His image, in the image of God He created him; male and female He created them" (Genesis 1:26).
At the time of creation, man and woman were a single entity. In the words of our sages, "one individual with two faces." However, God then said, "It is not good for man to be alone," because as a single individual, man lacked a partner, had no challenge, no potential for growth, and no creative power. So God divided man into two entities, male and female.
Why didn't He create them as two separate entities originally? Because as two, intrinsically two, each would be a prisoner of its own identity. The meeting of two would be, at best, a "relationship," and at worst, a war. Two would always be two.
That is why God created them as one and only later divided them in two. In this way, man seeks woman and woman longs for man. Thus, each has within themselves the power to observe their other half and discover in them the primordial unity. In this way, man and woman can remain faithful to one another and become a unity that is not a solitary and static singularity, but a creative and dynamic union."