How are public goods defined?

Public goods are defined as goods that are non-excludable and non-rivalrous. This means that once these goods are made available to the public, it is not possible to prevent anyone from using them, and one person's use of the good does not diminish the ability of others to use it as well.

For example, national defense is a classic public good; everyone benefits from it regardless of whether they contribute to its funding or not, and one person's enjoyment of security does not reduce the security available to others. This characteristic illustrates why public goods are often provided by the government, as the market may fail to provide them efficiently due to the free-rider problem, where individuals may benefit from the good without paying for it.

Understanding these characteristics is essential in economics as it highlights the role of government in providing and managing resources that benefit society as a whole.