Glycerin is a sugar alcohol, the simplest trivalent alcohol. The name glycerol was introduced because it has the correct ending -ol for an alcohol (the ending -in stands for alkine or amine).
Glycerol plays a central role as an intermediate product in various metabolic processes. It is used as a food additive under the symbol E 422.
https://de.wikipedia.org/wiki/Glycerin (Wikipedia CC-by-sa-3.0)