Lama Ole’s answer:
In tantric union practice, the main focus is to bring the male and female together to become “complete.” Of course we maintain our outward appearance, but on the inner and secret levels, we can quickly adopt the other gender’s qualities: men gain the intuition inherent in the women, and women obtain the strength of the men. On the deepest level, the man receives the space that transforms everything into something beyond personal, while the woman obtains the joy that rounds everything off.
The practice is very good if one is truly capable of doing it. Men and women can really complement each other that way. Women have certain energies in their bodies that contain different wisdoms and insights: There is a mirror-like wisdom which shows everything the way it really is. There’s an equalizing wisdom that shows the complexity of things. There is also a discriminating wisdom, a wisdom of experience, and an intuitive, all-pervading wisdom. If the man goes to the woman as if he is going to a temple, full of respect and dignity, if he opens up to her and is able to see her on a very high level, he will receive these wisdoms. If the woman approaches the man in same way, she will receive the four activities: the pacifying activity, the enriching activity, the fascinating activity, and the powerfully protecting activity.
On the deepest level, the female is like a lotus flower—warm, open, and happily holding something—while the male is like a diamond which enjoys radiating on its own. But a lotus that doesn’t hold anything and a diamond that doesn’t radiate for anybody are of no use. This is why it is important to bring the female and the male together. On the inner and secret levels, this encounter brings forth a complete human being.
But even if one has accomplished this, one still has desire for the other. Actually, once one has become liberated from hindrances and veils, one’s physical appearance might become more distinctly male or female and one’s ability to love becomes stronger. And on the inner and secret levels, there is great enrichment.