The Yarkovsky-O'Keefe-Radzievskii-Paddack effect (YORP effect or just YORP) is an effect on the rotation of asymmetric bodies such as asteroids. The effect is due to thermal radiation from the asteroid from the heat gained by radiation from the Sun. When the heated area turns away from the Sun, its outgoing radiation creates a force (e.g., Yarkovsky effect). In a symmetric body, the force will push the entire object, but in an asymmetric body, it can affect the object's rotation.
Binary YORP (BYORP) is an effect on two orbiting bodies orbiting each other and around a star, and affects binary (co-orbiting) asteroids. The YORP effect causes the orbit to expand or contract, depending on the particulars of the shape and orbit.