Ask who someone is
だれ is the question word for asking "who."
JLPTN5
だれ = who?~ wa dare desu ka
Who is [person/thing]?
Example Sentence

Who is he?
Use だれ to ask about a person's identity, in the same slot where the name or person would go in the answer. It works with the usual particles, and the more polite form どなた is used in formal settings. Like other question words, it does not change the word order of the sentence.
Tips and Common Traps
Build the Sentence
JLPT N5what is this?
Arrange the words in the correct Japanese order:
は
what it's about · said "wa" これ
this ですか
is it? (question) なん
what