Myths, symbolism, and folklore
Christmas tree: It is a conifer that nearly everywhere in the Christian world is decorated and lighted at Christmas time. It became customary in the nineteenth century (but probably goes back to heathen practices) for people to hang green branches and lighted candles in their houses as protection during the nights of 25 December to 6 January (the so-called Rauchnachte, when spirits were supposed to be abroad).
In Christendom the Christmas tree is a symbol of Christ as the true tree of life. The lights symbolize the "Light of the World" born in Bethlehem; the apples (often used as decoration) refer symbolically to the apple of knowledge in the Garden of Eden. The apple denotes original sin, from which Christ's act redeemed humanity, thereby giving humans access once again to paradise, symbolized by the Christmas tree. (Herder)