A lunar phase refers to the appearance of the Moon as seen from Earth, which changes over a cycle of about 29.5 days. This cycle includes several distinct phases: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent. Each phase results from the relative positions of the Earth, Moon, and Sun. The changing lunar phases occur because only a portion of the Moon's surface is illuminated by the Sun at any given time. As the Moon orbits the Earth, different amounts of its illuminated side become visible, creating the various phases. This cycle has been observed and recorded for centuries, influencing calendars and cultural practices worldwide.