A public good is a good or service that is both non-excludable and non-rivalrous.
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. Examples of private companies providing Public Goods include:
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.