The tragedy of the commons is a well known effect arising in game theory as a result of self-interested rational agents over-exploiting common good. While this arises in game theory, original concept comes from the XIXth century England. Those times it was customary for a village to have some small parcel of land, which could be used by villagers to let their cows graze. Over-grazing became commonly arising problem.
This problem applies more generally to any other common resource. For example, fish in the ocean, forests, public roads or even common fridge at work. If no rules or regulation is imposed, it is rational to deplete these resources and conserve private ones. This is extremely bad for the society. Hence it is named "tragedy".
It seems that Extra Credits found an interesting "sandbox" example in the realm of video games, which allows to see this tragedy in play from a different angle. This also allows to look for the solutions from a different perspective as well as teach further generations about what is wrong with our current state of affairs.