If your scoring meeple is the last player to moves to (or exceeds) the 6 space or the first player to reach the 24 space (spaces are marked with a sticker), you will immediately get an additional turn.
This means, that after this scoring phase, you immediately draw another tile and take another turn. Once your action is finished it's the next players turn.
Note: in both cases, if the placement of your tile causes another player's scoring meeple to reach or cross the Xmas logos, they will also get extra turns when it becomes their turns.