Hi Emily! 전세 is a housing rental contract for 2 years. On the other hand, 월세 is monthly rental contract. Both require a deposit which can be returned when you move out from the house. Usually, the deposit for 전세 is more expensive than deposit for 월세 since 전세 is long term contract, and doesn’t require any monthly fee. I heard 전세 is a special housing rental system that exist only in Korea. I hope this helps you.
Thanks so much for the kind explanation. It's very helpful. 고맙습니다.