In our tradition, this holiday represents the rebirth of the Sun King (or Oak King), and the death of the Holly King. The Holly King rules over the waning half of the year, from the Summer Solstice to the Winter Solstice, and the Oak (or Sun) King rules over the waxing half of the year—from Winter Solstice to Summer Solstice. During Summer Solstice (known as Litha), the cycle is reversed—the Holly King strikes down the Oak King in battle, and when the Oak King moves into the Underworld, the Holly King ascends to rule the season.
There are—and were—many holidays that take place during the winter months, including the Roman Saturnalia. But our traditions are more northern-European than Greco-Roman. Most of the decorations this time of year have their grounding in various pagan traditions, so truly, our Yule tree, is a Yule tree, and the lights and sparkle represent the return of the sun. One origin of Santa (well before Saint Nicolas) was the figure of the Holly King. So I decorate—for Winter Solstice, not for Christmas, using the modern representations of the decorations from the past that my pagan ancestors used. Lights instead of candles, ornaments instead of ribbons, etc..
The Winter Solstice is the longest night of the year. Held in late December, it is an astronomical event so the actual date can vary from year-to-year, but the holiday usually falls on December 21st or 22nd. Check your almanac and account for differences in time zones. It may fall on December 21st on the west coast, but December 22nd on the east coast.
During this time, we focus on togetherness, parties and festivities. Before the modern era—even in the 1800s and early 1900s, villages and towns were often cut off from one another by snow and ice. Entire families might go through the harshest part of winter without seeing another soul. If the harvest wasn't managed properly or if the crops had been scarce that year, people died from starvation.
And so Midwinter came to represent hope—for the return of spring, for the return of fertility and warm weather and planting season. In the far north, the sun actually disappeared--the longest night was truly the longest night with the sun barely peeking above the horizon. It is no wonder that in agrarian societies where everything depended on the success of the crops that the return of the sun each year was cause for celebration. The Gods had been kind--the source of life was re-emerging from darkness. With the Sun King reborn, the days lengthened and the season of growth once more overtook the land.
So what do we do? We hold ritual on the night before the Winter Solstice—the longest night of the year. We celebrate the rebirth of the Sun King to the Goddess, and the light from his brow strikes down the Holly King, and the cycle continues. The Goddess is eternal. The different faces of the Horned God are cyclic, going from birth to the zenith of his power to death to birth again. We drum, we dance, we chant, we make magic, we light candles to represent the glow of the sun, we invoke the gods, we continue to turn the Wheel.
Brightest Blessings this Yule,May Midwinter be gentle on you.
*some of this information was contained within my book Dancing With the Sun