What would be considered a public good?

A public good is characterized by two main features: it is non-excludable and non-rivalrous. This means that once it is provided, no one can be effectively excluded from using it, and one person's use does not diminish its availability for others. Examples include clean air, national defense, and public parks. Because of these characteristics, public goods are often provided by the government or through collective efforts, as the market may fail to supply them efficiently.