Lunar phases refer to the different appearances of the Moon as it orbits the Earth. These phases are caused by the changing angles of sunlight illuminating the Moon's surface. The main phases include New Moon, First Quarter, Full Moon, and Last Quarter, each representing a distinct stage in the lunar cycle. The complete cycle of lunar phases takes about 29.5 days, known as a lunar month. During this time, the Moon transitions from being completely dark during the New Moon to fully illuminated during the Full Moon, before returning to darkness. Each phase has unique characteristics and cultural significance.