The average distance between Earth and the Sun, about 150 million km, or 93 million miles, is called an astronomical unit. An astronomical unit is a way to measure distances in space using the average distance from Earth to the Sun.
Imagine you're trying to measure the exact distance between two cities on opposite sides of the country, but the highways and roads constantly change their paths due to construction. Just like the shifting roads make it hard to pinpoint a consistent distance, the Earth's orbit around the Sun is not a perfect circle, so the distance between them changes slightly throughout the year. The astronomical unit (AU) serves as a convenient "average highway" distance, representing the average path or distance, just as you'd calculate an average distance between cities despite varying routes.
