편 corresponds to "side" in English very closely, and 편이다 structurally matches "be on the side of". It is a weak statement of "Of the two, I'm on the side of ...", which extends to "tend to", "often", or "generally". 편이다 seems to be more natural and used much more widely than "be on the side of ..." though. Here are examples of how closely 편 and "side" match in different contexts: - 너는 아빠랑 엄마 중에 누구 편이니?: Whose side are you on, dad or mom? - 강의 저쪽 편은 숲이 우거져 있었다: The other side of the river was densely wooded. - 길 건너편에 편의점이 하나 있다: There is a convenience store across (on the other side of) the street. - 나는 잠을 잘 자는 편이다: I generally sleep soundly / I'm on the side of sleeping soundly. - 신나는 댄스 음악도 좋지만 발라드를 선호하는 편이에요. => Fast dance tunes are good too, but I'm on the side of preferring ballads.

A: 라닛씨는 댄스 음악과 발라드 중에 무엇을 선호하는 편이에요?(Which music does Mr Lanit tend to listen between dance music and ballad?) B: 신나는 댄스 음악도 좋지만 발라드를 선호하는 편이에요.(Although the exciting dance music is also good, I tend to listen ballad.) Quoted from http://www.koreangrammarplus.com/korean-grammar-int-%EB%8A%94%EC%9D%80%E3%84%B4-%ED%8E%B8%EC%9D%B4%EB%8B%A4-tends-to-often/ ~는/은/ㄴ 편이다 = Tends to, Often. This Korean Intermediate grammar point is used to express a TENDENCY rather than making an assertive and clear statement of a fact. One often uses words like 많이 (Many, A lot), 자주 (Very, a lot) etc. with this grammar point. After action verbs we use 는 편이다 After Descriptive verbs we use 은(if verb ends in a noun)/ㄴ(If verb ends in a vowel) 편이다 ~ 는/은/ㄴ 편이다 Example: 친구들과 전화를 자주 하세요? (Do you often call your friends) 응, 일주일에 세 번쯤 하니까 친구들과 전화를 자주 하는 편이야. (Yes, I call my friends about 3 times a week, i tend to call my friends a lot) 영화를 많이 보세요? (Do you watch a lot of movies) 네, 일주일에 두 번쯤 보니까 자주 보는 편이에요. (Yes, I tend to watch a lot of movies, about two times a week)