The Moon appears to change its shape daily because of its orbital motion around the Earth. As the Moon revolves around our planet, the amount of its sunlit surface visible from Earth changes. We always see the same side of the Moon, but the Sun illuminates different portions of this side throughout its orbit. This continuous change in the illuminated portion, as observed from Earth, gives rise to the various phases like new moon, crescent, half moon, gibbous, and full moon, completing a cycle in about 29.5 days.