it's ... thatA shortened form of 것은 바로, used to emphasize or identify the person or thing being described. It often corresponds to “what ... is” or “the one ... is.”
KO: 내가 가장 좋아하는 계절은 바로 가을인 건 바로 그 때문이야.
EN: That's exactly why autumn is the season I like best.