A double-decker bus is a type of bus that has two levels or decks for passengers. It is commonly used in urban areas to transport people efficiently, allowing for more passengers compared to single-decker buses. The upper deck often provides a better view of the surroundings, making it a popular choice for sightseeing in cities like London. These buses are typically designed with a staircase leading to the upper level and are equipped with large windows. Many double-decker buses are painted in bright colors and feature advertisements, contributing to the vibrant atmosphere of city life.