The RER B is a commuter train line in the Île-de-France region of France, connecting central Paris to the suburbs and beyond. It is part of the Réseau Express Régional (RER), which serves as a rapid transit system for the metropolitan area. The line runs from the northern suburb of Robinson to the southern suburb of Mitry-Claye, passing through key stations like Gare du Nord and Châtelet-Les Halles. The RER B is known for its importance in facilitating daily commutes for thousands of passengers. It connects with other transport systems, including the Métro and Tramway, making it a vital part of the public transportation network in Paris. The line is also used by travelers heading to Charles de Gaulle Airport.