 It changes the way that your jaw looks. Where a guy gives a square chisel look, which is supposedly what a lot of women always want in their guys. So you press your whole tongue against the roof of your mouth, keep your lips together, breathe through your nose and maintain a straight posture. They also have like metal things that they sell that you can put in your mouth and all do this. But in case you're wondering who's behind this trend, I thought this was fascinating.