There are many faces of love and many expressions of its binding aspect. Friendship and mutual companionship are definitely two of them. There are also bonds that form between a pet and its owner, a child and his parents, a patient and his doctor, a customer and a local shop owner, a flock and the shepherd, pupil and teacher. Each of these bonds are unique to themselves based solely on the particular relationship established between those whose bonds are formed.
Yet of all these, the one formed by the bonds of marriage is unique, and the one formed by Holy Matrimony even greater. It is the only one whose union naturally leads to the creation of a new rational creature with an immortal soul. Its fruitfulness is beyond comprehension.
This is the true reality behind what marriage is. It is absolutely not about the irrational, hence immoral, pleasure derived from the sexual act divorced from the act of procreation. It may well be the highest form of union God gave mankind.
Holy Matrimony is marriage blessed by Christ through His Church.