The transition state represents the highest energy point in a chemical reaction, while the product is the final outcome of that reaction.

According to the Hammond postulate, the structure of the transition state closely resembles the species that is nearest to it in terms of energy. This implies that if the reactants are more stable than the products, the transition state will bear a closer resemblance to the reactants. Conversely, if the products are more stable than the reactants, the transition state will resemble the products.

In the context of energy, the transition state appears as the peak on a reaction coordinate diagram. It signifies the stage at which the reactants have been sufficiently destabilized to initiate the formation of products, yet have not completely transitioned into the products. The transition state is characterized by its high instability and short lifetime, as it rapidly converts into the products.

In contrast, the product is the stable species that results from the completion of the reaction. The product is lower in energy compared to both the reactants and the transition state, which makes it more stable overall.

In summary, the transition state and the product are two distinct points on the reaction coordinate diagram. The transition state is the point of highest energy, while the product is the stable end result of the reaction, existing at a lower energy level.