A trundle bed is a type of bed that features a second mattress stored underneath the main bed. This lower mattress can be pulled out when needed, making it a practical solution for accommodating guests or maximizing space in a room. Trundle beds are often used in children's rooms or small apartments where extra sleeping space is beneficial. Typically, trundle beds come in various styles and sizes, including twin and full options. They can be made from different materials, such as wood or metal, and may include additional features like storage drawers. This versatility makes trundle beds a popular choice for many households.