Tree
Greco-Roman and Germanic rites used winter evergreens to signify life enduring darkness (i.e. remaining green during the dead of winter).
The modern Christmas tree tradition began in 16th-century Germany, popularized by Martin Luther. It spread through Europe and North America in the 18th & 19th centuries.
Wreaths similarly represent life in the winter, and also symbolize the cyclical nature of time & the promise of renewal.
Nativity
Nativities are direct representations of the birth narratives found in the Gospels of Matthew & Luke and are arguably the most iconic element of Christmas given its historic roots. Nativities were non-verbal depictions intended to make the Scripture accessible & inspire devotion among the laity (illiterate).
Francis of Assisi's 1223 Greccio celebration is the first key reference for live tableaux. Read more about Francis & the first Nativity Scene
Hand-crafted Nativity sets evolved into common household devotionals in Catholic Europe. Now nativities are commonplace in Christian homes worldwide during the Christmas season.
Star
The star derives from Matthew's Gospel as the celestial sign guiding the Magi. It commonly tops evergreen Christmas trees in modern traditions.
It has been depicted historically as a single bright star, but some other explanations include a comet or planetary conjunction. Angels are also sometimes referred to as stars in biblical poetry (Job 38:7; Isaiah 14:13; Revelation 1:20).
The Christmas star theologically represents divine guidance & the visual shorthand for the Incarnation.
Gifts
Gift-giving is anchored in the biblical Magi bringing gold, frankincense, and myrrh. Traditions of Santa Claus giving gifts to children are inspired by St. Nicholas of Myra, a 4th-century bishop known for his generosity.
Pre-christian traditions like Saturnalia & Yule were blended into Christmas gift-giving customs. This helped preserve practices compatible with Christian theology.
The tradition was solidified in the 19th century into a child-focused family gift exchange.
Lights
Candles and fires at midwinter long predate Christianity pointing towards the sun's return. Christianity interprets them as signs of Christ: "Light of the World."
Tree candles and window lights developed in early-modern German Protestant homes. Electric lights later allowed this symbol to become widespread and safe.
Santa
St. Nicholas of Myra (4th century) is the source of the Santa Claus figure. Known for his generosity, he inspired gift-giving traditions during Christmas.
Nicholas eventually merged (conceptually) with Dutch-American "Sinterklaas" and European gift-bringer folklore. 19th-20th-century media later established the secular, red-suited North Pole figure.