The reason behind this is that these rites are meant to be working with the Goddess, who represented by the moon.
The actual process of performing the esbat can be summed up very concisely. The witch or coven will gather at a designated ritual space. There, they will cast a circle, and perform rites that will raise their magickal and psychic power, and then direct that power at their desired goal. Since there are so many variables as to what a witch or group of witches may wish to direct their energy, it is difficult to offer up an example of what these rites may entail.
However, one of the things that is a common theme among esbats is that it is a time for connecting and communing with Deity. This is often done by the reciting of The Wiccan Rede and The Charge of the Goddess while in circle. Afterwards, time may be spent in either meditation or performing acts of divination with tarot cards, runes or other means. This is followed by a communion of cakes and wine, where the gathered witches will celebrate their coming together and catch up on the previous month and make plans for the coming one. Then the ritual circle is opened, the leftover cakes and wine are offered up to Nature, and the witches will go their separate ways.
1 2