M31, also known as the Andromeda Galaxy, is the nearest spiral galaxy to the Milky Way and is located about 2.537 million light-years away from Earth. It is one of the largest galaxies in the Local Group, which includes the Milky Way, Triangulum Galaxy, and about 54 other smaller galaxies. M31 has a diameter of approximately 220,000 light-years and contains around one trillion stars. The Andromeda Galaxy is visible to the naked eye from Earth, appearing as a faint, smudgy patch in the night sky. It is expected to collide with the Milky Way in about 4.5 billion years, leading to the formation of a new galaxy. M31 is an important object of study for astronomers, providing insights into galaxy formation and evolution.