The document explains the phases of the moon, which change gradually over a cycle of about a month due to the moon's orbit around the Earth and its reflection of sunlight. It describes the eight recognized phases, including new moon, first quarter, full moon, and third quarter, highlighting how the perspective from Earth affects our view of the moon's illumination. Additionally, it touches on the moon's gravitational influence on ocean tides, which results in the regular rise and fall of water levels.