Number one, that Christ is the head of man and man is the head of woman. Relationship number two, that man is the glory of Christ and the woman is the glory of man. So man is the glory of Christ, and Christ is man's head ruling over him. In the same way, the woman is the glory of man, and man is her head ruling over her.
Now, this headship order between man and Christ has existed since the beginning of man, but this headship between the man and woman does not appear to have always been in place in the same way as it is now. It was only after Adam followed Eve into sin, bringing the whole earth under a curse that God ever said to Eve, "Your desire shall be for your husband, and he shall rule over you."