This grammar pattern is used to provide an information before asking a question. In the second clause, question can be made by considering with the point in the first clause. It serves to make the sentence sound more soft.
● 여기는 아직 봄인데 거기는 어때요? (It’s spring here; how about there?)
● 저는 한식을 좋아하는데 혜리 씨가 좋아하는 음식은 뭐예요? (I like Korean food; what is hyeri’s favorite food?)