The traditional planets -- Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn -- have a very important thing in common: they're all visible in the sky to the naked eye. Their light was extremely important to ancient astrologers. Some even called astrology the "science of light.”
To these skywatchers, the Moon divided the cosmos between the celestial sphere of the planets and the Earth. From her heavenly throne, the Moon protected and comforted humanity, as well as brought the divine messages from the other planets down to Earth.
As the Moon moves through the sky, she meets up other visible planets, gathers their light and carries it down to Earth. From the time she makes her last major aspect to one of these visible planets until she enters the next zodiac sign, we say the Moon is "void-of-course." When the Moon is void, there are no messages to carry. The world is still.
Imagine a beach. The waves rolling in to shore are like the Moon's normal course. They bring seaweed and driftwood from the ocean. You can surf on them. Between the waves, the sea is calm. You can float or rest. You can fix your surfboard. You can even paddle in to shore, but there's no helping push from the sea; you have to work harder. The sea-between-waves is like a Moon void-of-course.
Moon void-of-course is an excellent time to catch up, regroup, and rest. You may want to make space to listen, write or reflect. It isn't the best time to start something new, because you may have to work harder to get the project off the ground.
Usually the Moon is void from a few minutes to a few hours every two and a half days. But on very rare occasions, void Moons can last 24 to 48 hours. During these extended voids, consider setting aside time for your own quiet retreat, even if you're just turning off your phone ringer. All things need rest to function well, and a Moon void is nature's time out.