It's a nativity scene where you put one piece of the puzzle together each day (starting on December 1st) and by Christmas you will have made a complete nativity scene. There is a scripture and an activity to do on each puzzle piece too. You can find the complete instructions and the original source on the lds.org website HERE.
What a great way to keep Christ in Christmas. For more Christ centered Christmas ideas (from videos to music to quotes to children's activities) you can check out the resources found HERE.