Glycerin soaps are soaps that contain glycerin, a component of fat or oil. They are recognizably different from other soaps because they are translucent. The clarity is due to the alignment of the soap molecules, which can be induced through the addition of alcohol and sugar.
Glycerin soaps are considered to be one of the most moisturizing types of soap. The unique quality of this type of soap allows it to be both moisturizing and effective for all different kinds of skin. The benefits of glycerin soap help your skin become healthy and moisturized.
Source: wikipedia, livestrong.com