라고 (and another related word 다고) is a quoting form. It's used when relating someone's remark or some statement or fact that is not one's own. It attaches to a word or phrase that is passed around to indicate that it is not something the speaker has created (but you can quote your own saying in some special cases). 1. 누구라고 해요? (usually shortened to 누구래요?) = 누구라고 말해요? = (전화한 사람이) 누구라고 말해요?. A. 누구예요? = Who are they? A direct question asking the person who answered the call - this may not be appropriate if the answerer is not in a position to know that. B. 누구라고 해요? / 누구래요? = Who do they say they are? This asks what the caller said to the answerer - it's a more proper question. 2. The two have the same meaning, but again, 뭐라고 is more natural. A. 여기에 뭐(를) 써야 돼요? B. 여기에 뭐라고 써야 돼요? It's hard to differentiate the two in English translation, but B is a better way to say it because it is clearer and more in line with how people speak. If the context is not given, 써야 in A can be ambiguous (as 쓰다 means to use as well as to write), like "What should I use/write here?". B has no chance of misinterpretation because 라고 makes it clear it's about some information to put down. Here's another example illustrating the same point: - 뭐? = What? (it might mean "So what?", "What about it?", "What do you mean?", or "What did you say?") - 뭐라고? = What did you say? (clear - it can only mean one thing)

there is no big difference. just depends on situation. 1. I usually say . 나는 ** 에요. 저는 ** 입니다. but when you ask A about B, you'd better say 'B 는 누구에요 ?' we don't say ' B는 누구라고 해요 ?' or if B is an object (not person), you can use 'B는 뭐라고 불러?' 2. 여기에 뭐 써야해요 ? 여기에 뭐라고 써야해요? both are correct.