(CNN) So you've heard of a blood moon, and maybe even a blue moon, but what about a black moon?

The phenomenon is occurring again in North America on July 31 -- the first one since 2016. The rest of the world will have to wait until August 30.

But, what does this even mean? Why is it important? Here's everything you need to know about this astronomical event.

Wait, what is black moon?

A black moon is basically the second new moon of the month , something that rarely occurs. It works similarly to a Leap Year. A lunar cycle typically takes about 29 days to complete, but our months are slightly longer. So sometimes, about every 32 months, we happen to get two full moons or two new moons. The second full moon in a month is called a blue moon, and the second new moon is called a black moon.

Read More