A suction cup is a device that creates vacuum pressure to adhere an object onto another surface. It typically consists of a flat, round base with a flexible ring around its circumference and a small opening on top connected to the interior space within the ring. When air is removed from the interior space by creating a vacuum through the small opening, the flexible ring contracts and creates a strong grip against the surface it's attached to. Suction cups are commonly used for holding objects in place or as a means of attachment without damaging the surfaces involved.