Demand and need are two different economic categories that are both related and different under the condition of commodity currency relationship. Need refers to the material products, spiritual products and services that people are willing to get for survival, development and enjoyment. The need for material products can be divided into the need for means of production and means of subsistence. The needs of means of subsistence can also be divided into the needs of subsistence, development and enjoyment. Demand refers to actual demand, regardless of whether people have the purchasing power of these products and services.
Supply refers to the quantity of goods that the seller can and is willing to provide to the buyer at a certain price in a certain period of time, including goods and services on the market and inventory goods that can be provided to the market in time. Market supply can be divided into material products, spiritual products and services. In capitalist society, there is also the supply of labor goods.