Slippers, shoes without uppers in the second half, are generally worn indoors. Usually refers to the three protrusions that pass through the shoe or foot only, or the direction of the shoe and foot is parallel to the sole of the foot, or the approximate plane where the inner surface of the sole is located and coplanar with the extension of the calf axis without harming the shoe or the foot. Shoes that can separate shoes from feet and slippers have been widely used in people's daily life.