Public Goods

A public good is a good that is non-rivalrous and non-excludable.

Non-rivalry means that consumption of the good by one individual does not reduce availability of the good for consumption by others

Non-excludability means that no one can be excluded effectively from using the good.
In the real world, there may be no such thing as an absolutely non-rivalrous and non-excludable good; but economists think that some goods approximate the concept closely enough for the analysis to be economically useful.

Common examples of public goods include: defense, public fireworks, lighthouses, clean air, street light.

Law enforcement, streets, libraries, museums, and education are commonly misclassified as public goods, but they are technically classified in economic terms as quasi-public goods because excludability is possible, but they do still fit some of the characteristics of public goods.

Private Good

A private good is defined as "an item that yields positive benefits to peopleā€ that is excludable and rivalrous

Excludable means that its owners can exercise private property rights, preventing those who have not paid for it from using the good or consuming its benefits.

Rivalrous means that consumption by one necessarily prevents that of another.

A private good, as an economic resource is scarce, which can cause competition for it.

Examples include food, clothing and property/asset owned by an individual.