네요

oh — remarking on what you just noticed

Reacts to something the speaker is discovering right now, said out loud to the person in front of them: 사람이 정말 많네요 'wow, there really are a lot of people today', 처음이네요 'this is actually my first time'. It carries mild surprise or admiration, which is why it fills reaction shots and interviews. 구나/군요 does a similar 'ah, I see' job but sounds more like thinking to yourself, while 네요 is aimed at your listener. Drop the 요 (많네) with friends.

Register: polite; 네 without 요 is casual