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 black-body radiation from the asteroid from the heat gained by radiation from the Sun. When the heated area turns away from the Sun, its emitted radiation creates a force (e.g., Yarkovsky effect), which is strongest from the surface just rotated away from the Sun. In a symmetric body, the force will push the entire object, affecting its orbit, but in an asymmetric body, it can affect the object's rotation.
Binary YORP (BYORP) is an effect on two orbiting bodies that are orbiting each other, the pair orbiting around a star, and affects binary (co-orbiting) asteroids. The created force and resulting acceleration causes the orbit of the two around each other to expand or contract, depending on the particulars of the shapes and orbit.