Public good

Is a good that is both non-excludable and non-rivalrous.

A commons good is a such as wild fish stocks in the ocean, which is non-excludable but rivalrous to a certain degree. If too many fish were harvested, the stocks would deplete, limiting the access of fish for others.

Public goods problems are often closely related to the "free-rider" problem, in which people not contributing (ex. paying or other) for the good may continue to access it. Thus, the good may be under-produced, overused or degraded. Public goods may also become subject to restrictions on access and may then be considered to be club goods; exclusion mechanisms include toll roads, congestion pricing, and pay television with an encoded signal that can be decrypted only by paid subscribers.

Like with commons public goods require governance. they are usualy managed by public institutions, such as governments (local, regional, national or even international). This is in stark difference from nondominum goods, which do not require protection from any institution.