An Astronomical Unit (AU) is a standard unit of measurement used in astronomy to describe distances within our solar system. It is defined as the average distance from the Earth to the Sun, approximately 93 million miles or about 150 million kilometers. This unit helps astronomers communicate distances in a more manageable way, especially when dealing with vast spaces. Using the AU, scientists can easily compare distances between celestial bodies. For example, the distance from the Earth to Mars is about 1.5 AU, while Jupiter is roughly 5.2 AU from the Sun. This system simplifies calculations and enhances our understanding of the solar system's structure.