Sabbats and Esbats

Sabbats

There are eight festivals through the year called Sabbats. The four Greater Sabbats are: Imbolc, Beltane, Lughnnasa, and Samhain. The four Lesser Sabbats are the equinoxes and solstices: Ostara, Litha, Mabon, and Yule. The eight Sabbats represent seasonal birth, death, and rebirth. In them witches honor the Goddess and her cohort, the God.

During the equinoxes the flow of power is stronger; whereas, the solstices are a time for regrouping energy. The celebration of solstices and equinoxes is done on a particular day when the sun changes into particular signs. The Greater Sabbats are celebrated on specific days too. There are two ways to determine the holy days: 1) on a definite day, or 2) on the closest full moon. Since the ancient pagans counted nights instead of days, all their festivals were celebrated on the eve or the night before. The day began at sundown.

As I mentioned before, the Sabbats are time to honor the deities and the change of seasons. It is not necessary to perform magick during them. However, many witches find it fructuous to do so, specially if the time is right for a certain spell or to do divination. Then again, this may vary among traditions.

Esbats

Esbats are nights used by the witch to perform magick. After all we all need a time to raise energy, cast spells, perform healing, etc. You must take into consideration the phases of the moon before performing your works. Esbats are also known as Lunar Rituals. Perhaps the two most well-known Esbats are New Moon and Full Moon celebrations. During Full Moon celebration, the witch performs the Drawing Down the Moon. It is done to empower oneself.

information taken from:
D.J. Conway's Celtic Magic
Scott Cunningham's Wicca: A Guide for the Solitary Practitioner
Silver RavenWolf's To Ride a Silver Broomstick