An economy consists of the economic system in a certain region, comprising the production, distribution or trade, and consumption of goods and services in that region or country. An economy is the total aggregate sum of all transactions of value between two agents, such as one individual to one other individual, or between groups of individual activity, such as in organizations to other organizations, and between one nation and another nation. Transactions only occur when both parties agree to the value, commonly expressed in some currency, or price. Then and only then is the sale of good or service acted on in the transaction. An economy represents the diverse activity of all agents engaged in the production of valuable goods and services for other agents in the economy.