"The Commons" are all resources that are commonly held right to by all people. Some lands are considered part of the commons, but the term is best applied to items like Air and Water.
That's recent liberal horseshit propaganda. "The commons" refers to a feudal land use practice first explained by William Foster Lloyd:
Tragedy of the Commons: The Concise Encyclopedia of Economics | Library of Economics and Liberty
The rational explanation for such ruin [the tragedy of the commons] was given more than 170 years ago. In 1832 William Forster Lloyd, a political economist at Oxford University, looking at the recurring devastation of common (i.e., not privately owned) pastures in England, asked: Why are the cattle on a common so puny and stunted? Why is the common itself so bare-worn, and cropped so differently from the adjoining inclosures?
Lloyds answer assumed that each human exploiter of the common was guided by self-interest. At the point when the carrying capacity of the commons was fully reached, a herdsman might ask himself, Should I add another animal to my herd? Because the herdsman owned his animals, the gain of so doing would come solely to him. But the loss incurred by overloading the pasture would be commonized among all the herdsmen. Because the privatized gain would exceed his share of the commonized loss, a self-seeking herdsman would add another animal to his herd. And another. And reasoning in the same way, so would all the other herdsmen. Ultimately, the common property would be ruined.
Liberals have tried to transform the terminology into meaning that "the commons" is something sacred that the government should regulate. Originally it was meant to demonstrate precisely the opposite, that common ownership should be abolished wherever possible.
Indeed. I believe it was his attempt to warn people of the unintended consequences of the Voter Reform Act of 1832. That was the first of I think three (can't remember) Reform Acts that saw the eventual destruction of the Empire.