The neutralized form of gluconic acid. It's a great ingredient to neutralize metal (especially iron and copper) ions in a cosmetic product. This helps to prevent discoloration of the formula over time or rancidity of cosmetic oils. It can also be a pH regulator and a humectant (helps skin to cling onto water).
It's also used in oral care products where it reduces the bitterness of other ingredients. And it's natural, both Ecocert and Cosmos approved. (source: manufacturer info)