What is the Sacrament of Holy Matrimony? What does this Sacrament do?

First we must define what is a sacrament. A Sacrament is an outward sign of inward grace, instituted by Christ for our sanctification. Or in other words, A Sacrament, in this case Marriage by a man and a woman who have been sacramentaly baptized, is an outward sign of inward grace, (grace being God's enabling power to live out the sacrament of Marriage), instituted by Christ for our sanctification ( the two being set apart to grow in grace and in charity toward each other).