Let's break it down:
* Se is a particle that indicates "from," "by," or "with."
* Kaun means "who."
* Hai is the present tense form of the verb "to be."
The phrase is usually used in situations where someone is pointing to a person or object and asking for their identity.
Here are some examples of how you could use "se kaun hai?" in a sentence:
* Se kaun hai? (Who is that?) *pointing at a person*
* Se kaun hai jo bahar khade hain? (Who is that standing outside?)
* Se kaun hai jo phone pe baat kar rahi hai? (Who is that talking on the phone?)
It's a common and versatile phrase that can be used in many different situations.