The term 'Paris Tube' is a reference to the Paris METRO, which is the rapid transit system in Paris, France. It is also known as the Reseau Express Regional (RER) and is operated by the RATP Group. The Paris METRO consists of 16 lines and over 300 stations, making it one of the largest METRO systems in Europe. The term 'Paris Tube' is often used interchangeably with the term 'Paris METRO' to refer to the same system.