Moon phases in the occult; it’s not exactly a secret. I’ll start right off the bat by saying that Lunar phases and the positions of the Moon aren’t that important- not anymore than the average planet in any case, depending on the magical system you practise.
Lunar placements (so waxing, waning etc.) is primarily used in Witchcraft and Wicca (as far as I know) and to a slightly lesser extent, pagan forms of magick e.g. folk magick.
For those that are unfamiliar with this concept:
Regardless of which magickal system, Moon phases increase the potency of a working when it comes to primarily clairvoyance or clandestine workings; all things of an “occult” nature. To a lesser extent, the general things people seek in life (money, love etc.)
In general, a waxing Moon is for obtainment or increasement, and waning is for destruction in these matters or decreasement regarding effect/severity.
For more information: