A by-product is a supplementary or secondary product (arising as the result of a process) whose value is a small relative to that of the principal product. In the timber industry, for example,...
War and Peace, the made-for-television dramatization of the Leo Tolstoy novel of the same name
An example of a product is anything you can buy in the store
For example, if you make a strawberry cake, the by-products can be:-leaf of a strawberry-wrappers-leftover strawberries
For example, product differentiation might be necessary when a new laundry detergent is advertised.