A substitutable product or good refers to a similar item that can be used in place of another product or good, providing consumers with a comparable alternative. This means that the substitutable product or good serves the same purpose and satisfies the same need as the original product or good, but may differ in terms of brand, price, or other characteristics. The availability of substitutable products or goods allows consumers to have a choice and can also drive competition in the market, ultimately benefiting the consumer.