A monopoly refers to an industry where there is only one player. They control the entire or most of the market as no one else provides the service they provide, sell the goods they sell and even if they do, can’t compete with them. Many countries have laws that restrict monopolies from operating.
For example…
Commuter trains are a monopoly in many cities as no other train operator exists to transport passengers on the rail. Whether they are run by the government or private companies, building rail lines and associated equipment is no easy feat for inter-city train operators. However, with the emergence of operators like Virgin Trains and a “disruption” mindset that has become expected of late, maybe metro trains won’t be a monopoly for too long.