Soy milk is a replacement for real milk, for those who either can't stomach lactose or are vegan. Soy milk contains no animal fat (so no cholesterol) and actually has fiber, unlike regular milk. Brands include Edensoy and Westsoy (this author prefers the former).
Dr. Weil (drweil.com) claims that drinking soy milk is a way of "getting all the benefits of cow's milk, without the problems"
A web page extolling the benefits of soy can be found at http://www.mayohealth.org/mayo/9705/htm/soy.htm
Soy milk can be made at home by adding 1 part soy flour (not toasted) to 3 parts boiling water, simmering for 20 minutes, and straining.