Newton's Law of Gravitation describes the gravitational force between two masses, stating that it is proportional to the product of their masses and inversely proportional to the square of the distance between them. Kepler's Laws of planetary motion explain how planets orbit the sun in elliptical paths, with specific rules governing their speed and distance from the sun. Orbital motion is influenced by these gravitational forces, dictating the behavior of celestial bodies in space. J.B. Tatum's "Celestial Mechanics" is recommended as a resource for understanding these concepts, though it is noted that it may not be widely available in paperback. Exploring additional literature on celestial mechanics can further enhance comprehension of these fundamental principles.