Supply and demand describe the relationship between how much of something is available and how much people want it. This relationship is part of markets. It affects how goods and services are bought and sold.

When a product such as fruit or fuel is widely available, supply is high. When many people want the same item, demand is high. Prices in shops or markets often reflect these changes. This pattern can be seen in markets around the world.

Supply and demand are used in economic systems. They are observed in everyday buying and selling.