A public good is a good or service that is both non-excludable and non-rivalrous.
Pure Public Goods are valuable things (goods, information, services, etc) that cannot charge money. For example, clean air is a public good because if you pay for a factory to install pollution reducing mechanisms I get cleaner air for free. The factory cannot reduce the pollution you breathe without also reducing the pollution I breathe. [Optimism]
As Vitalik Buterin notes, when economists' definition of Public Goods interacts with the real world "in almost any specific case there are all kinds of subtle edge cases that need to be treated differently. A park is a public good. But what if you add a $5 entrance fee? What if you fund it by auctioning off the right to have a statue of the winner in the park's central square?" [Vitalik]
The definition of a Pure Public Goods is therefore insufficient to make funding decisions. "Most things are not pure public goods: they are some hybrid in the middle, and there are many dimensions on which they could become more or less public that do not easily map to "exclusion"" [Vitalik]
However, Private Companies can offer both Pure and hybrid Public Goods. The term Public Good is typically utilized to characterize resources. [Chaomons] Some examples:
Satellite imagery
Private companies such as Google and Maxar Technologies provide satellite imagery that is used for a variety of public purposes, such as mapping, disaster relief, and environmental monitoring.
Open-source software
Private companies such as Google and Facebook provide open-source software that is used by millions of people around the world, including government agencies and educational institutions. Google created TensorFlow. Facebook created llama. Merkle Manufactory created Farcaster.
Medical research
Private companies such as Pfizer and Moderna invest billions of dollars in medical research, which leads to new drugs and treatments that benefit everyone in society.
Renewable energy
Private companies such as Tesla are developing and deploying renewable energy technologies that help to reduce greenhouse gas emissions and combat climate change.
Philanthropy
Private companies and their foundations often donate money to support public goods such as education, healthcare, and environmental protection.
Future Topics:
Public Goods Funding
What constitutes a Public Good for Protocols such as Farcaster and Optimism?
Pure Public Goods vs Impure Public Goods
Public Goods vs Common Goods