there are simple examples. 1. I finished my work. or I've done my work. 나는 일을 "끝냈다." he closed the report yesterday. 그는 어제 레포트를 "끝냈다." when you or other people ends something you can say 끝내다. 2. my work is finished. 내 일이 "끝났다." time's up. 시간 "끝났어." when something is ended, you can say 끝나다. and plus, there is similar casual usage. 끝내주다. it means awesome or hot. ex) 그 여자 몸매가 끝내준다. her body line's really hot. 음식이 끝내줘요! this food is awesome! (or tasty!)

vi. 끝나다 (the word don't need to have a object) vt. 끝내다 (the word need a object)