"Who" is a pronoun used to refer to people or individuals. It helps identify or inquire about someone, often in questions or relative clauses. For example, in the question "Who is coming to the party?" the word "who" seeks to identify a person. In grammar, "who" is often contrasted with "whom," which is used in more formal contexts to refer to the object of a verb or preposition. Understanding the correct usage of "who" and "whom" can enhance clarity in communication, especially in written language.