면서

while doing something else at once

Marks two things one person does at the same time: 수영을 하면서 즐거운 시간을 보냈어요 is "we had a great time while swimming", 실수하면서 배워 is "you learn by making mistakes". The two actions must share a subject. Attached to a description it means the thing is both at once — 짭조름하면서 is "salty and at the same time…", leading into another flavour. Also handy for narrating what you were thinking during an action: 하면서 '어…?' is "while doing it I was like, uh…?". After a consonant-ending stem it is spelled -으면서.