Unfortunately, the world is not such a kind place. Each one of us has limited resources, and we must make choices as to how we will use those resources. The science of economics is concerned with the rationing of scarce resources.
Scarcity occurs when, at a zero price, quantity demanded is greater than quantity supplied.
In other words, if the good were free, there would be a shortage of the good because more of the good would be demanded than supplied. Most goods and services are scarce. The concept of scarcity suggests the necessity of rationing goods and services in some manner. The most common way to do this is by using the price system. When a price is put on a good or service, people have to choose what products they will spend their income on.