A pronoun, as you all know, is a word which stands in place of another.

John kicked the can.
He kicked it.

However, let’s suppose we wanted to find out the name of the person who kicked the can. We don’t know so we need to use a pronoun which could stand for anyone (or anything, etc). In other words, we need an Interrogative Pronoun.

Who kicked the can?
What did he kick?

Basic Information

The basic interrogative pronouns then are:

Who made it to the top?
Whom did they hire for that job?
Which would you rather watch?
What was his reaction when he saw them?
Whose trainers are these?

Simply put:

• who, whom and, sometimes, which are used to ask about people
• who is used when it acts as the subject of a verb, while whom is used when it acts as the object
• which and what are used to ask about things and animals
• whose is used to ask about the owner of something

notes

• which and what can also be used as interrogative adjectives
• who, whom and which can also be used as relative pronouns

The compounds forms whoever,whomever,whichever, and whatever are also interrogative pronouns.

Useful Links

Questions‏‎ in English Grammar – making questions in English

Who-What-Where-When-Why-How‏‎ – the question words in English

Interrogative Adjectives in English Grammar – about which and what used slightly differently

Relative Pronouns in English Grammar – about who, whom and which used slightly differently