은 적 있다

have done something before

적 means 'an occasion', so -(으)ㄴ 적 있다 says the experience has happened at least once: 이 이야기 전에 들은 적 있어요? 'have you heard this story before?', 아버지한테 밥상에서 한 번 맞은 적 있거든? 'I got smacked at the dinner table by my dad once'. The negative is 적 없다 'have never'. It is about lifetime experience, not the recent past — for what you did yesterday you would just use the past tense. Six of these lines are 들은 적 있다, asking whether someone has heard something.

Register: neutral; very common in questions