Esbats

In addition to the eight Sabbats observed every year, most modern Wiccans and Pagans celebrate a regular Esbat, in which magic is performed and the goddesses of the tradition are honored. Most covens and groups meet at least once a month, and time this ceremony so it coincides with the full moon.
The word Esbat is of French origin, from s'esbattre, which loosely translates to "frolic joyfully."

The Esbats (pronounced Es-bat) are the Wiccan Full Moon Celebrations.
There are 12 - 13 Full Moons yearly or one every 28.1/4 days.
The Moon is symbolic of the Goddess, as well as a source of energy.
Each Moon has a traditional name.
Each Full Moon has a different meaning and magickal purpose. Because of this, it is a good idea to plan your Full Moon Rituals to work with the meaning and purpose of the Moon. The Full Moon is also a traditional time for divinations of all kinds, as the power of the Moon aids in such work.

One key source of this practice is the “Charge of the Goddess”, which states in part, "Whenever you have need of anything, once a month, and better it be when the moon is full, you shall assemble in some secret place and adore the spirit of Me Who is Queen of all the Wise."

Charge of The Goddess was written by
Gerald Gardner and  Doreen Valiente