Product is referred to as one resulting from a chemical reaction material. A starting material is known, however, as a reactant (or reactants outdated: the starting material ).
At a reaction one or more products may be produced. Besides the desired main product, often caused by-products that may be used otherwise.
Is a reaction in the equilibrium state, the products can also be called a reactant, and vice versa. The distinction between a reactant and product is therefore arbitrary in the case of an equilibrium reaction.