Commerce is the business of trading money or product for money or product.  This is primarily the buying and selling of product as opposed to the trade or barter of a product or service.  Commerce replaced the barter system as a more efficient and effective manner to gain what one wants in a timely and effective manner.

In commerce, a business trades a service or a product for money, which can be spent on another service or product.  This completes the supply verse demand circle.  These services or products are produced within the business as product based upon the demand of the customer.  These customers do not need to be the final customers of the product, simply a customer who is willing to purchase the product.  It is very common for a business to purchase partial products from another business to alter them and resell them.  This is the case with many products such as deodorant and diaper wipes.  The initial business runs the packaging, a second business labels them, and the third business fills the product.  This can be done without the product ever being in the hands of the business that it is made for, but rather sold directly then to the grocers and distributed around the world.

The commerce practice is a replacement of the barter program, which required both parties to want or need something from each other.  If either party did not have a product that was desired by the opposite party, no bartering takes place.  With the invention of currency, there is no more need for a product and therefore both parties can engage is commerce.