A by-product is a secondary product that is generated during the manufacturing or processing of a primary product. For example, when producing corn syrup, the leftover corn husks can be considered a by-product. These by-products can sometimes be used in other applications, reducing waste and increasing efficiency. By-products can also occur in natural processes. For instance, during photosynthesis, plants produce oxygen as a by-product while converting sunlight into energy. Understanding by-products is important for industries and the environment, as they can lead to new opportunities for recycling and sustainable practices.