you mean in english... teacher kim when did you came in here? i think 김 선생님이 언제 (여기에) 왔었어요... in this case you have two past tense (do-present, did-past) (come-present, came-past) in korean presentence verb+아요,어요,해요... i think you already know that. so in present 오다 to come into past tense 오+았요= 왔어요... then you have one past tense again "did" in present is do in korean 있다 past-- 었다 so thats why 왔었어요.. i hope you get what i mean?

*-였다 : past which happened already and still it stayes or effects on the present time *-였었다 : past which happened already but very different from the present situation or doesn’t effect on the present More precise explanation is in the post right below. :) http://www.coreanbigsis.com/korean-grammar-past-tense-expression/#more-409

I think Lee got a good point.:D Looking at both sentences, 1) 김선생님이 어제 여기 왔어요. 2) 김선생님이 어제 여기 왔었어요. The first sentence is a general description meaning "something happened in the past" but nobody knows if he is still in the same place or not but chances are he is still here while the second sentence means he came here yesterday and he left meaning he is not here. Secondly the second sentence could be an emphasis on the action which is "CAME". Here is another example of it. 1) 눈이 왔어요 - just a general description, we don't know whether it melted away or not. 2) 눈이 왔었어요 - it means it has already melted away, so that you can't see the snow anymore, and I think it's more like "pernah" in your language. ^____^

'왔어요'는 김선생이 현재 와서 아직도 안 간 상태이고, '왔었어요'는 김선생이 이미 왔다가 간 상태입니다. 왔어요 = Kim came and still stay here. 왔었어요 = Kim came but left here.