I have seen during the Mixed Double olympic tournaments in Pyeongchang that some team can start the end with the pre-placed stones not in the center position but from a side. This is called "Power Play".
What are the advantage to this situation?
There are two "classical" strategies in Curling:
1) With the hammer (i.e. the right to play the last stone in the end), your goal is to draw the game to the side of the house, so that at the end you can "easily" place your last stone in the house (hoping to score more than one point).
2) Without the hammer, you try keep the play near the centre of the house, ideally with a centre guard in front, aiming at limiting the opponent to only one stone or even "steal" a stone.
The normal set-up in Mixed-Doubles is a centre guard and one stone in the house. If you play a good first stone (which means you do not have the hammer), you position yourself in the house behind a guard, the ideal start if you want to steal. Thus the normal set-up gives a slight favour to the team without the hammer.
Both teams can once in a match choose to have the "power play" set up when they have the hammer. Thus starting the game with the "classical" corner guard and keeping the centre clear. The idea is then of course to score at least two stones in this end.
How often this is actually done and how high the success rate is I cannot say.
By having the stone in the house and the guard in the corner and not in the center it is more likely that the team with the hammer will be able to score 2 or more points and therefore will not attempt blanking the end. That in turn makes the game more exciting for fans.