The term 'trade by exchange' can be summarized as bartering, which is a form of trading goods or services without the use of money. Bartering has been used for centuries as a way to exchange goods and services between two parties. It is often used in situations where money is not available or when one party does not have enough money to purchase what they need. Bartering is still used today in some parts of the world, especially in rural areas where money is scarce.