Interrogative and indefinite pronouns
Interrogative pronouns are pronouns used to ask questions. Indefinite pronouns are the same question words, but used as placeholders in statements. For example, in English we use the five w’s + h: who, what, why, when, where and how. These words can be used to ask questions like, “Who is there?” or “Where did you go?” In such cases, they are functioning as interrogative pronouns. But these same words can also be used as placeholders in statements. “You are not who I thought you were.” “Where you go, I will go.” In these examples, the same words are functioning as indefinite pronouns.
Hebrew has just two interrogative / indefinite pronouns, and you have already learned them: מִי (“who”) and מָה (“what” or “how”). These words do not change form.