이 used for something close to you but far for the other person 그 used for something close to the person you are asking but far from you,( also used for something that is not where you are) 저 used for objects far from you and the one you are asking

이, 그 and 저 are used with nouns to mean 'this, it and that' respectively. 이 나무 = This tree 그 집 = That house (It) 저 산 = That mountain 이 사과 맛있어요 = This apple is delicious 저 사과도 맛있어요 = That apple is delicious, too.