The New Moon occurs when the Moon is between the Earth and the Sun, and the side of the Moon facing the Earth is not illuminated by the Sun. This phase marks the beginning of the lunar cycle.
As the Moon moves in its orbit, a small sliver of the illuminated portion becomes visible, marking the Waxing Crescent phase. The Moon appears to be growing in size.
The Full Moon occurs when the Moon is on the opposite side of the Earth from the Sun, and its face is fully illuminated by sunlight. This phase marks the middle of the lunar cycle.
The Waning Crescent phase occurs as the Moon continues to wane towards its New Moon phase. Only a small sliver of the illuminated portion remains visible, and the Moon appears to be shrinking in size.