During a new moon, the light reflecting off the moon's surface from the sun is completely blocked by the position of the earth, creating a moon that is generally visible only through a telescope.
The earth and moon have now moved to allow direct reflected sunlight onto the moon's surface. A crescent-shaped lit section of the moon is now visible on its right side.
The moon's surface is now receiving enough light from the sun to allow its right half to be visible from the earth. The moon is now a quarter of the way through one lunar cycle.
Roughly three quarters of the moon's surface is now reflecting the sun's light, with only a crescent on the moon's left side darkened.
The entire surface of the moon is now reflecting the sun's light, producing a perfect sphere. The moon is now halfway through its cycle.
Roughly three quarters of the moon's surface is now reflecting the sun's light, with a darkened crescent on its right side.
Half of the moon can now be seen, with its bright side on the left. This is the opposite positioning to the moon's earlier first quarter phase. The moon is now three quarters through its cycle.
The moon now only has a crescent of light visible on its left side, and roughly three quarters of its surface cannot be seen. In a few days, the moon will complete its cycle as it moves back to its initial new moon phase.