Also Called K-Meta or K2S2O5 or potassium pyrosulfite is used as a preservative and sanitizer in wine making industry. It is a white crystalline powder with a pungent smell of Sulphur. This smell is because of SO2 being released. When in tablet form it is called Campden.
You can use either name as long as the potassium metabisulfite is stored in cool dry condition it will release SO2 that can be used as a wine sanitizer or to kill bacteria and wild yeast in the fresh grape juice.