A sofa bed, also known as a sleeper sofa or convertible sofa, is a piece of furniture that combines the functionality of both a sofa and a bed. It typically features a mattress that can be easily pulled out from within the frame of the sofa for use as a bed. This type of furniture is often used in small living spaces or guest rooms where space is limited, but both seating and sleeping accommodations are needed. The sofa bed can quickly convert from a comfortable sitting area to a cozy place to rest, making it an ideal solution for those who entertain frequently or have overnight guests.