According to Investopedia, a public good is characterized by being nonexcludable and nonrivalrous. This means that no one is barred access from its use, and an individual can consume the product without reducing its availability to others. Private goods are the opposite, as they are both rivalrous and excludable.
Examples of public goods include national defense, public parks and radio broadcasts. Experts say that public goods are susceptible to the free-rider problem, which exists when individuals do not contribute to the provision of the goods. This most often occurs because people can experience the benefits of the goods with or without contribution, such as not paying taxes but utilizing public services funded by those taxes.