Final answer:
In a chemical equation, the substances listed on the left side of the arrow are called Reactants, which are the starting materials of the reaction, while those on the right are known as Products, the end result of the reaction.
Step-by-step explanation:
The term that describes each substance on the left side of the arrow in a chemical equation is Reactant. Reactants are substances that enter into a chemical reaction and are found on the left side of the reaction equation, preceding the arrow. On the other hand, the substances on the right side of the arrow are called Products, representing the substances that result from the reaction. The number that appears before a reactant or product in a chemical equation is referred to as the Coefficient, which signifies the number of molecules or moles of the substance involved in the reaction.