When you learn Korean, you will hear terms like formal, polite and honorific. I want to explain this to you in this post.
Formality is about situation. You use formal endings like -습니다, -는다 when you have business meetings, presentations or ceremonies. For normal situations(non-formal) like talking to family, friends or people who you know well, you can use -아/어/여요 or -아/어/여.
Politeness is about listener. When you talk to someone who is older that you or higher position, you should use polite endings like 습니다 or 아/어/여요. When you talk to someone who is the same age as you or younger, you will use -는다 or -아/어/여.
비가 왔습니다. (formal, polite : news anchor)
비가 왔어요. (non-formal, polite : a kid to a mom)
비가 온다. (formal, non-polite : writing a diary, news paper, books)
비가 와. (non-formal, non-polite : between friends or to young people)
Honorific forms are used when a subject is a person who is older generation or higher position while politeness is about listener. You will use -(으)시 after verbs and adjectives. For example,
You can study honorific forms by clicking here.
One more thing, 저 and 나 both are ‘I’ or ‘me’. 저 is humble way which is polite, 나 is non-polite. So if you use 저(I,me), you’d better use -(스)ㅂ니다 or -아/어/여요. On the other hand, if you use 나, you can use -ㄴ/는다 or 아/어/여.