Badnjak is a special Christmas tradition in Serbia where people go out to their nearby forests and carefully select a young oak tree that is considered the "badnjak". This is done a few days before Christmas Eve, and the tree is then cut down with a special axe and then carefully carried home or transported on a truck.
Once at home, the tree is cleaned and stripped of its smaller branches, and then put into a holder or decorated with ribbons or other decorations. The Badnjak is then ready to be taken to the church and burned as part of a special Christmas Eve service.
During the service, the Badnjak represents the idea of welcoming the baby Jesus into the home and hearts of the people. The burning of the Badnjak represents lighting the way for the baby Jesus to find his way to people's homes.
In short, Badnjak is a special Christmas tradition in Serbia where people carefully select and decorate a tree, and then burn it during a special Christmas Eve service to symbolize welcoming the baby Jesus into their hearts and homes.