The demand for labor is a "derived demand".
This means that the demand for labor is not a direct demand for labor itself, but rather it is derived from the demand for goods and services that labor can produce. In other words, businesses hire workers because they need them to produce the goods and services that they sell.
For example, if a business sells pizzas, it will need workers to make the pizzas, deliver the pizzas, and serve the customers. The demand for labor in this case is derived from the demand for pizzas. If the demand for pizzas increases, the demand for labor to produce and deliver the pizzas will also increase.
Therefore, the demand for labor is closely tied to the demand for the goods and services that labor produces, and it is derived from that demand.