ther early Christmas Trees, across many part of northern europe, were cherry or hawthorn plants (or a branch of the plant) that were put into pots and brought inside, so they would hopefully flower at Christmas time. If you couldn't afford a real plant, people made pyramids of woods and they were decorated to look like a tree with paper, apples and candles. Sometimes there were carried around from house to house, rather than being displayed in a home.
It's possible that the wooden pyramid trees were meant to be like Paradise Trees. These were used in medieval German Mystery or Miracle Plays that were acted out in front of Churches on Christmas Eve. In early church calendars of saints, 24th December was Adam and Eve's day. The Paradise Tree represented the Garden of Eden. It was often paraded around the town before the play started, as a way of advertising the play. The plays told Bible stories to people who could not read.