the.com/christmas tree

means An evergreen tree cut down and brought indoors to be decorated with lights and ornaments as the centerpiece of Christmas celebrations.

from The custom traces to Germany, where 16th-century households brought decorated evergreens indoors, often tied to guild and family traditions around the winter solstice and Christmas; a popular legend credits Martin Luther with first adding candles to mimic stars he saw through fir branches, but this is folklore, not documented history. The tree stayed largely a German custom until the 19th century, when German immigrants carried it abroad and royal and fashionable households in Britain helped popularize it more widely — after which it spread rapidly as a mainstream Christmas fixture.