https://www.youtube.com/watch?v=eQJjveGGG68
i did my homework
i've done my homework
--> i did my homework. and now my homework is done
i lived in Korea for 20 years - 과거
i've lived in Korea for 20 years - 현재완료 (과거의 일에 대한 현재에 상태)
i've been lived in Korea for 20 years - 현재 완료 진행형
과거 완료 - 과거의 어떤시점을 이야기 할때 그전에 어떤 일이 이미 일어 난경우에 사용
when i graduated 10 years ago, i have already started working
when i got back home last night, my parents had already gone to bed
I started working in 2005.
