what's the difference between '갔어' and '갔었어'?
what's the difference between '갔어' and '갔었어'?

since the -았어 conjugation in 갔어 already implies past tense, is -았었어 like past perfect tense in english?

Question

what's the difference between '갔어' and '갔었어'?
what's the difference between '갔어' and '갔었어'?

since the -았어 conjugation in 갔어 already implies past tense, is -았었어 like past perfect tense in english?

Answer

hmmmm... It's difficult to explain... because we don't use past perfect tense commonly.

먹다.  - 먹었다. - 먹었었다. (x)
present   past     p.p.

If we use past perfect tense  that is only we want to say about "some experience".

가다. - 갔다. - 갔었다.
go       went    (been)

너  미국 갔었어?   Have you ever been to USA?

너 이거 먹었었어? Have you ever eaten this?

Answer

"집에 갔었어요."  과거완료or 대과거 ------> Past perfect tense 

"집에 갔어요."   직전에 과거, 과거 -------> Past tense.

둘다 집에간건 같은데 어느정도의 과거냐의 차이,  갔었어요는 과거에 행한 일이 완료되있음

--->  They both imply the past tense but" 갔었어" happened a long ago like past perfect tense in English.