In Korean personal pronouns are not used if its clear whom we talk about.

For example:
좋아해요? Do (you) like (it)? 너는 좋아해요?

Plural is also omitted if the number is clear.

For example
숲에는 나무가 있다 “wood-in tree-the exists” 숲에는 나무들이 있다

Korean (informal polite)	Korean (formal polite)	English	Remark
나	저	I	1st person, singular, nominative
내, 나의	제, 저의	my	1st person, singular, genitive
너	당신 (dang-sin) *	you	2nd person, singular, nominative
네, 너의	당신의*	your	2nd person, singular, genitive
이 사람	이 분	this person close to me	3rd person singular
그 사람	그 분	that person close to you	3rd person singular
저 사람	저 분	that person over there	3rd person singular
그(사람)들		these persons close to you	3rd person plural

(*) very careful with using 당신 please, it is rarely in direct conversation.
When used with strangers, this sounds rude and offensive

In Korean, it’s more natural to refer to people by their names or titles (e.g., 선생님 seon-saeng-nim for “teacher”) rather than using pronouns like in English.
To address unknown strangers, it’s polite to also use 선생님 seon-saeng-nim for “teacher”