잘가 = Goodbye. This is the common, informal way to say goodbye, but there are other ways to say this for different situations.
When being formal, one would say 언녕히 계세요 or 언녕히 가세요.
The difference between these two words is one character (which changes the meaning entirely) so it can be confusing.
There are two ways because there are different ways to say goodbye depending on who is leaving.
When you are the one leaving (and the person you’re talking to is staying), say the first one, 언녕히 계세요.
- 계세요 means “please stay,” so the phrase means “Please stay peacefully.”
- If you want to say it casually, say 잘 있어 or “Stay well.”
When you are seeing someone else off, say 언녕히 가세요
- 가세요 means “please go,” so the phrase means “Please go peacefully.”
- The casual version would be 잘가, aka the most common way to say goodbye.