Today, the Moon, second brightest object in the sky, has reached the New Moon phase, which means that it is directly between the Sun and Earth, and thus invisible for us Earthlings as of now.
As for lunar mechanics, the Moon is always half lit. The reason we don't always see it as such is thanks to orientation in relation to us. Right now, with the Moon directly between us and the Sun, we don't see any of the lit side, thus making the Moon invisible to us as seen from Earth.
After today, we will see more of the Moon each night as its lit side turns more toward from us and heads toward a new lunar cycle.