The single most-used politeness marker: tacked onto the end of almost anything, it makes it polite without making it formal. What is striking in these clips is that it goes on bare fragments, not just full sentences — 정말요? "really?", 잠시만요 "one sec", 카레소스랑요? "with the curry sauce?", 동현이는요... "as for Donghyun...". Drop it and the same words become 반말, the blunt form used with close friends; add it and they are safe with strangers. It is a step below 습니다/ㅂ니다, which is the stiff formal register used for announcements and to superiors.
Register: polite but not formal; default in everyday speech