This is why humans don't live on the moon.
From the Earth's point of view, we always see the same side of the moon, which indicates that the moon doesn't rotate at all (relative to our position).
The moon takes 29.5 days to revolve around the Earth. The Earth takes 365.25 days to rotate around the Sun.
We say that a day is the amount of time it takes for a celestial object to rotate on it's axis. In the case of Earth (relative to the sun), it indicates how long it takes the Sun to 'rise again'.
How long is a day on the moon?
1) 1 Earth day
2) 29.5 Earth days
3) 365.25 Earth days
4) The moon doesn't rotate. A day is forever.