the whole moon

less than half

half

it depends

dark because the lit side is facing away from us.

dark because it is not getting any light from the sun.

dark because the Earth is blocking the light from the sun.

bright because it is reflecting light from the sun.

the sun shines on different areas of the moon.

the Earth sometimes gets in the way of the sunlight.

it travels at different speeds around the Earth.

we see the illuminated side at different angles as the moon goes around the Earth.