DEFINITIONS
A Product is a group of several Items or SKUs.
B2B example: An entire line of Bic Pens can be interpreted as a product.
Pens in Blue color are one item, and pens in red can be another item.
B2C example: A shirt is a product. Each size (S,M,L,XL) might have different
SKU numbers, and each one of them constitutes a different item.