The Christmas tree dates all the way back to pagan times. Then, long before Christ was born, many people worshipped Gods and Goddess's of nature, like the Sun God and Mother Nature. To these pagans,light and green of the tree were signs of hope that, even in winter, nature was not dead. Mistletoe and holly, 2 other plants that stay green thoughout the year, were also used in midwinter pagan festivals.
The friendly rituals of Christmas are often customs that are connected with the holiday, they are not actually part of the festival beliefs of any Christian church. For example, as we have said, evergreen and lights from 'torches', oil lamps bonfires - were used in pagan festivals to show that life continued through winter. Most people who place lights on Christmas trees are copying the ancient pagan ritual without quite knowing why. However, people today do not just follow this ritual without any reason. It is likely that we share with those who lived thousands of years ago the feeling that a tree and lights are a cheerful festive sight.
from: Ocean Harmony