안녕하세요. means ‘Hello’ when you meet someone. It is very polite, so you can use anyone. Between friends(the same age), you can just say 안녕 which is very casual.
When you say ‘Good bye’, there are two different ones. If you leave, you will say ‘안녕히 계세요’ which means ‘Stay well’. If you stay, you will say ‘안녕히 가세요’ which means ‘Go well’.
When you both leave like on the street, you both say ‘안녕히 가세요’, whereas when you hang up the phone, you both say ‘안녕히 계세요’.
Let’s practice 안녕하세요. 안녕히 가세요. and 안녕히 계세요. with these videos.
안녕히 계세요. Stay well, good bye.
안녕히 가세요. Go well, good bye.