Joella Rivera they were talking about Baekhyun's hapkido skills, like the high kick he did in his solo so Xhen said he is really good in hapkido. Baekhyun was then telling them main points about it, like the move (don't know what move he said) can break limbs so rest of members were laughing thinking he is joking so he was saying that he is telling truth and not joking this time at all, like for real you can break limbs. So basically he talked about hapkido and how good he is.