The Moon is Earth's only natural satellite and is the fifth largest moon in the solar system. It orbits Earth at an average distance of about 238,855 miles (384,400 kilometers) and has a diameter of approximately 2,159 miles (3,474 kilometers). The Moon's surface is covered with craters, mountains, and flat plains called maria, which were formed by ancient volcanic activity. The Moon plays a crucial role in influencing Earth's tides due to its gravitational pull. It goes through phases, such as the new moon and full moon, as it orbits Earth, which affects how much of its surface is illuminated by the Sun.