The moon goes through different phases as it orbits the Earth. These phases are caused by the changing positions of the moon, Earth, and Sun. The main phases include the new moon, first quarter, full moon, and last quarter. Each phase lasts about 29.5 days, creating a cycle known as the lunar month. During a new moon, the moon is between the Earth and the Sun, making it invisible from our perspective. As it moves, more of its surface becomes illuminated, leading to the waxing crescent, first quarter, and waxing gibbous phases. After the full moon, the illumination decreases, resulting in the waning gibbous, last quarter, and waning crescent phases.