Insecticides are organized into classes-organophosphates, carbamates, pyrethroids, neonicotinoids, etc.- that share a common chemical structure and mode of action (MOA). MOA is the specific process by which an insecticide kills an insect, or inhibits its growth. Target site of action is the exact location of inhibition, such as interfering with the activity of an enzyme within a metabolic pathway. MOA and target site of action are often used interchangeably in practice and are combined as MOA in this learning module.