Yule was the winter solstice celebration of the Germanic pagans. In Germanic Neopaganism it is one of the eight solar holidays, or sabbats, where Yule is celebrated on the winter solstice: in the northern hemisphere, circa December 21, and in the southern hemisphere, circa June 21.
"Yule" and "Yuletide" are also archaic terms for Christmas, sometimes invoked in songs to provide atmosphere. Indeed, this is the only meaning of "Yule" accepted by either the full Oxford English Dictionary or the Concise Oxford Dictionary, and people unfamiliar with ancient pagan traditions will not distinguish between Yule and Christmas. This usage survives in the term "Yule log"; it may also persist in some Scottish dialects.
Of the contested origin of Jól, one popular but factually unlikely connection is to Old Norse hjól, wheel, to identify the moment when the wheel of the year is at its lowpoint, ready to rise again. Linguists suggest that Jól has been inherited by Germanic languages from a pre-Indo-European substrate language and either borrowed into Old English from Old Norse or directly inherited from Proto-Germanic. Other instances refer to the ancient gaulic word "helle" which means light. We thus find half of the word Noël.
A far more likely origin for the term "Yule" can be traced from the Old English/Anglo-Saxon term "Géol", which is strongly connected with the word for yellow - "geol". One may see the evolution of this word for yellow throughout the Germanic and Scandinavian countries: German "gelb", Norwegian "gul", Danish "gul", Dutch "geel", Swedish "gul", Frisian "giel", even Italian "giallo", Lithuanian "geltonas" and Romanian "galben". The Old English Géol became the Middle English "Yole" and finally modern Yule, whereas the word geol or geolu evolved to become modern yellow. This same divergence of words also occurred in the other languages mentioned. All of these terms ultimately stem from the Indo-European root "ghel-" meaning "to shine". Since the Yule festival is native to the northern European lands, where midwinter is a time of short days and little light, it is a strong possibility that the original sense of Yule as a midwinter festival had much to do with "bringing back the sun" and creating bright, shining, yellow sun-and fire-themed decorations and festivities. Another connection may be to the brightness of the sunlight glaring off the white snow, i.e. "Géolmonad" = "Shining Month" or "Bright Month".
In the Scandinavian Germanic languages, the term Jul covers both Yule and Christmas, and is also occasionally used to denote other holidays in December, e.g., "jødisk jul" or "judisk jul" (tr. "Jewish Yule") for Hanukkah. The word "jul" has also been borrowed into the neighboring Finnic languages, most notably to Finnish and Estonian (where it has been modified to "joulu" and "jõul" , respectively, and denotes Christmas in modern usage), although the Finnic languages have a linguistic origin different from Germanic languages. In Old English, geóla originally referred to the month of December. The meaning later narrowed to mean Christmas with the coming of Christianity in Anglo-Saxon England.
In Russian, there is a word that refers to fir trees that is associated with yuletide. Other Slavic languages have similar words as well.
What is certain, is that Yule celebrations at the winter solstice predate Christianity, and though there are numerous references to Yule in the Icelandic sagas, there are few accounts of how Yule was actually celebrated, beyond the fact that it was a time for feasting. 'Yule-Joy', with dancing, continued through the Middle Ages in Iceland, but was frowned upon when the Reformation arrived. It is, however, known to have included the sacrifice of a pig for the god Freyr, a tradition which survives in the Scandinavian Christmas ham.
The confraternities of artisans of the 9th century, which developed into the medieval guilds, were denounced by Catholic clergy for their "conjurations" when they swore to support one another in coming adversity and in business ventures. The occasions were annual banquets on December 26,
"feast day of the pagan god Jul, when it was possible to couple with the spirits of the dead and with demons that returned to the surface of the earth... Many clerics denounced these conjurations as being not only a threat to public order but also, more serious in their eyes, satanic and immoral. Hincmar, in 858, sought in vain to Christianize them" (Rouche 1987, p. 432).
Many of the symbols associated with the modern holiday of Christmas such as the burning of the Yule log, the eating of ham, the hanging of boughs, holly, mistletoe, etc. are apparently derived from traditional northern European Yule celebrations. When the first missionaries began converting the Germanic peoples to Christianity, they found it easier to simply provide a Christian reinterpretation for popular feasts such as Yule and allow the celebrations themselves to go on largely unchanged, rather than trying to suppress them. The Scandinavian tradition of slaughtering a pig at Christmas (see Christmas ham), and not in the autumn, is probably the most salient evidence for this. The tradition derives from the sacrifice to the god Freyr at the Yule celebrations. Halloween and Easter are theorized to have been likewise assimilated from northern European pagan festivals.
English historian Bede's Historia ecclesiastica gentis Anglorum ("Ecclesiastic History of the English People") contains a letter from Pope Gregory I to Saint Mellitus, who was then on his way to England to conduct missionary work among the heathen Anglo-Saxons. The Pope suggests that converting heathens is easier if they are allowed to retain the outward forms of their traditional pagan practices and traditions, while recasting those traditions spiritually towards the one true God instead of to their pagan gods (whom the Pope refers to as "devils"), "to the end that, whilst some gratifications are outwardly permitted them, they may the more easily consent to the inward consolations of the grace of God". The Pope sanctions such conversion tactics as Biblically acceptable, pointing out that God did much the same thing with the ancient Israelites and their pagan sacrifices.
In Germanic Neopagan sects, Yule is celebrated with gatherings that often involve a meal and gift giving. Further attempts at reconstruction of surviving accounts of historical celebrations are often made, a hallmark being variations of the traditional blót.
Groups such as the Asatru Folk Assembly in the US recognize the celebration as lasting for 12 days, beginning on the date of the winter solstice.
In particularly Wiccan-influenced and New Age religions attempts at reconstruction are largely disregarded and the festival is largely only related to historical accounts by name, as a part the Wheel of the Year.
The holiday is observed in a manner that commemorates the death of the Holly King identified with the wren bird (symbolizing the old year and the shortened sun) at the hands of his son and successor, the robin redbreast Oak King (the new year and the new sun that begins to grow) (Farrar & Farrar  1998: 35-38).
Because Christmas happens during extreme summer temperatures in the southern hemisphere, a few Australians celebrate a second festival, known as Yulefest, at the southern winter solstice in June. A much more popular winter celebration is "Christmas in July", not surprisingly celebrated (several times by some) in July, removing the celebration from all religious connections both Pagan and Christian.
Though notionally synonymous with Christmas, both religious and secular, Yule and Yuletide are sometimes used by English speakers as secular names for December 25th and late December in general in much the same way that the Scandinavian "Jul" does not distinguish between the Germanic Pagan feast, Christmas, and (quite possibly) the pre-Indo-European winter solstice celebration.