This is actually a super useful particle that you’ve already been using without knowing it! The 시 particle shows up in 안녕하세요, with the literal break down of it being 안녕 meaning peace and 하세요 (하다 + 시 + 해요체 honorific form)
One thing about Korean many people struggle with is the dynamics between people and speech. For native English speakers; especially if English if your only language, formalities is something that doesn’t exist to a quarter of the extent as in Korean. Korean is a culture based highly around respect and knowing or understanding you position and others.
Now Koreans don’t solely use these terms for people related to them, they are used freely! People call the woman running the restaurant 이모, boys call their older friends 형, etc. This terms are used to show how close and familiar you are with others (and for the ‘aunt’ at your favourite K-BBQ to warm up to her and maybe get extra side dishes haha).