Who is a word we use to ask about or refer to people. When you don't know someone's identity, you ask “Who is that?” When you want to know which person did something, you ask “Who ate the last cookie?”

The word helps us identify people in stories and conversations. In Charlotte's Web, Wilbur asks “Who are you?” when he first hears Charlotte's voice. When your teacher says “Who can answer this question?” she's asking which student knows the response.

Who also connects descriptions to people. The phrase “the girl who loves astronomy” tells us something specific about which girl we're talking about. “The scientist who discovered penicillin” identifies Alexander Fleming without using his name.

People sometimes confuse who with whom, a version used in formal writing. For everyday conversation and most writing, who works perfectly fine. You might hear whom in very formal situations or older books, but who is what you'll use almost every time you're asking about or describing a person.