SKU (Stock Keeping Unit) is a product code that you can use to search and identify stock on hand from lists, invoices, or order forms. It is a term that is typically used when talking about inventory management.
UPC (Universal Product Code) is a type of code printed on retail product packaging to help in identifying a particular item. It consists of two parts – the machine-readable barcode, which is a series of unique black bars, and the unique 12-digit number beneath it.
One of the key differences between these two is that SKU is used internally by the team/company and is unique to individual retailers whereas UPC is used externally and remains the same throughout the product's shelf life.