On the "How We Make Soap" page we explained that when the sodium hydroxide (lye) and liquid are mixed with the oils during the initial soap making stage, a chemical process called saponification begins.
The term saponified means the oils and sodium hydroxide/liquid solution have bonded together, neutralizing the sodium hydroxide and combining the ingredients into soap.
Superfatting is the process of adding extra fats (oils or butters) when formulating a soap recipe, so there is more fat in the mixture than the lye can react with during the chemical reaction.
Superfatting leaves a portion of unincorporated oils in the finished soap. Superfatted soaps have superior moisturizing and emollient qualities.