What Does -(으)면서 mean in Korean?

-(으)면서 indicates that the actions of the first and second verbs occur simultaneously. It means ‘while’ in English. When the verb stem ends in a vowel or ㄹ，-면서 is used, and when it ends in a consonant, -으면서 is used.

Example:밥을 먹으면서 TV를봅니다.I eat while watching TV.

운전하면서 전화하지 마세요. 위험해요. Don’t use the phone while driving. It’s dangerous.

Pay attention that the subjects of both clauses are the same. That is, they must be the same person.

하영 씨는 노래를 하면서 재준 씨는 피아노를 칩니다. (wrong)

(하영 씨는) 노래를 하면서 (하영 씨는) 피아노를 칩니다. (correct)

(Hayeong) plays the piano while she (Hayeong) sings.

When the subjects of the two verbs are different, -는 동안 is used.

하영 씨기 노래를 하는동안 재준씨는 피아노를 칩니다. (correct)

While Hayeong sings, Jaejun plays the piano.