Glycerin, or glycerol, is a sweet-tasting, thick liquid that can be dissolved into water and alcohol. It is derived from both plants and animals, since it is found in all living things. There are also ways to artificially produce it, but they are not very cost effective.
Glycerin is an excellent solvent, and many nutrients will dissolve in it more easily than they do into water or alcohol. We dissolve some of these nutrients into a small amount of glycerin, then dissolve that glycerin solution into purified water, ethanol, or both.
When frozen, glycerin become gummy, which makes it a common base for candies. It’s also used in soaps and lotions to soften skin.