This is Ammonium Acetate. "Ac" stands for the acetyl group,
COCH3. The NH3 is ammonia, which is actually protonated to NH4+, so
the actual formula is NH4-O-COCH3.
NH3OAc is the chemical formula representing ammonium acetate, which is a salt composed of ammonium and acetate ions. It is commonly used in laboratory settings as a source of acetate ions and a buffering agent in various chemical reactions.