Quoted from https://sydneytoseoul.wordpress.com
Proceded by either who, what, why, when, where, whether or how, this ending connects a clause the requires additional information. Corresponds to 'whether or not A/V' in certain cases.
너무 맛있었어요! 어떻게 만들었는지 가르쳐 주세요.
It was delicious! Please tell me how you made it.
여자 친구가 있는지 없는지 궁금해요.
I wonder whether he has a girlfriend.
청소하는지 쉬는지 잘 모르겠어요.
I don't know whether she is cleaning or resting.
내일 날씨가 더운지 알아요?
Do you known whether tomorrow's whether will be hot?
While you can transform verbs into nouns but using +기, you can also use -는 것.
We add it to the verb stem when using present tense. For past tense we use -(으)ㄴ 것, and for future tense use -(으)ㄹ 것.
For example, taking the base verb 공부하다:
공부한 것 = what you studied
공부하는 것 = what you study
공부할 것 = what you will study
편지를 받는 것을 좋아해요
I like receiving letters
요즘 일하는 것을 어디예요?
Where is it you are working recently?
운동하기는 건강에 좋아요
Exercising is good for your health