Transilien is a network of suburban trains that serve the Île-de-France region, which includes Paris and its surrounding areas. Operated by SNCF, the national railway company of France, Transilien connects commuters to various destinations, making it easier to travel to and from the city. The Transilien network consists of several lines, each identified by a letter and color. These trains are designed to accommodate daily commuters, providing frequent service and convenient access to major hubs, including La Défense and Gare Saint-Lazare.