Products exist on two levels: the product and product format.
The product represent top-level information on an item. This includes things that are common to every purchasable version of this product:
This represents a purchasable version of the product:
physical music format - Vinyl, CD
digital format - MP3
clothing size variant
There may be multiple product formats on every product. These are listed on the product page for the customer to select from.
It is also possible to list individual format and link through to a dedicated format page.