A "metro" is a type of rapid transit system that operates in urban areas, providing efficient transportation for commuters. It typically consists of underground or elevated trains that run on dedicated tracks, allowing for quick travel between different parts of a city. Many major cities around the world, such as New York City, Paris, and Tokyo, have their own metro systems to help reduce traffic congestion and pollution. Metro systems are designed to be accessible and affordable, often featuring multiple lines that connect various neighborhoods and key locations. They usually operate on a fixed schedule, with frequent service during peak hours. Passengers can purchase tickets or use smart cards for easy access, making the metro a popular choice for daily commuting and tourism.