Barter is a system of exchange where goods or services are directly traded for other goods or services without the use of money. This age-old practice involves a mutual agreement between parties who have something of value to offer each other. In a barter transaction, both parties must find each other's offerings desirable, creating a system of reciprocal trade. While less common in modern economies where currency is the primary medium of exchange, barter systems still exist, often in niche markets or informal arrangements. It relies on the principle of double coincidence of wants, where both parties involved must have something the other desires for a transaction to occur.