A serial number is a unique identifier assigned to an individual item, often used for tracking and inventory purposes. It helps manufacturers and consumers distinguish one product from another, even if they are of the same model. Serial numbers can be found on various items, including electronics, appliances, and vehicles, and are typically printed on labels or engraved on the product itself. These numbers are crucial for warranty claims, repairs, and recalls, as they allow companies to identify specific items. For example, if a defect is discovered in a batch of smartphones, the serial number helps pinpoint which devices are affected, ensuring efficient resolution.