Ephemerides are tables or data sets that provide the positions of celestial bodies, such as planets, moons, and stars, at specific times. They are essential for astronomers and navigators, helping them predict the locations of these objects in the sky over time. These calculations are based on the laws of celestial mechanics and can be used for various purposes, including astrology, space missions, and satellite tracking. Ephemerides can be generated for different time frames, from daily to yearly, and are crucial for understanding the movements of objects in our solar system and beyond.