Lunar phases refer to the different appearances of the Moon as observed from Earth, which change in a cyclical pattern over approximately 29.5 days. This cycle includes phases such as the New Moon, First Quarter, Full Moon, and Last Quarter, each representing varying amounts of sunlight reflecting off the Moon's surface. These phases occur due to the relative positions of the Earth, Moon, and Sun. As the Moon orbits Earth, the sunlight illuminates different portions of its surface, creating the beautiful and familiar cycle of lunar phases that has fascinated humanity for centuries.