The set of quantities that buyers are willing and able to purchase at each price refers to what?

The definition provided in the question pertains directly to the concept of the Demand Curve. The Demand Curve represents the relationship between the price of a good and the quantity of that good that buyers are willing and able to purchase. As prices change, the demand curve reflects how this affects consumer behavior: typically, as prices decrease, the quantity demanded increases, and vice versa. This relationship is often depicted graphically, where price is plotted on the vertical axis and quantity demanded on the horizontal axis, illustrating a downward-sloping curve.

The Demand Curve is essential in understanding market dynamics because it helps businesses and economists analyze consumer preferences and behaviors in relation to price fluctuations. This information is crucial for making decisions about pricing, production levels, and inventory management.