What is the difference between monthly rent (월세) and key money deposit (보증금) in Korea, and how does the jeonse system work?

Wolse (월세) is monthly rent with a smaller deposit (보증금), usually a few million to tens of millions of won, returned when you move out. Jeonse (전세) has no monthly rent but a very large lump-sum deposit that the landlord holds and returns in full at the end, keeping the interest as their benefit. For any large deposit, protect yourself by registering your lease (전입신고 plus 확정일자) at the community center and considering deposit guarantee insurance (전세보증보험), and always check the property registry (등기부등본) before signing.