A baby crib is a piece of furniture that is designed to provide a safe and comfortable sleeping environment for babies. It typically consists of a base frame, mattress, mattress cover, side rails, and a canopy. The base frame is usually made of wood, metal, or plastic and is designed to provide a sturdy, rigid structure that will not collapse when a baby is inside. 

The mattress is usually made of foam or other soft materials, and the mattress cover is designed to protect the mattress from dirt and spills. The side rails are designed to prevent the baby from falling out of the crib, and the canopy is designed to provide shade and protection from the sun. All of these components work together to create a safe and comfortable environment for a baby to sleep in.