The market process is generally modeled using the economic concepts of supply and demand. The plans/desires of consumers are embedded in the concept of demand and the plans/desires of producers in the concept of supply. The plans of these two types of economic actors are brought together in markets, which are the entities in which transactions occur. In a modern economy, markets do not require that the buyers and sellers meet in a geographic place, so markets no longer require actual "marketplaces."

The concept of demand represents the market activity of consumers. Demand is defined as the quantity of a good or service that consumers will be both willing and able to purchase at any given price during a specific period of time, holding all other factors constant. Demand is, therefore, a relationship between price and quantity demanded. Many factors other than...