who and whom

The difference between “who” and “whom” is the same as the difference between “I” and “me;” “he” and “him;” “she” and “her;” etc. Who, like other pronouns such as I he, and she, is a subject. So, it is the person performing the action of the verb. On the other hand, whom, acts like me, him, and her in a sentence. It is the object. Therefore, it is the person to/about/for whom the action is being done.

Who should be used to refer the subject of a sentence.

Who likes cheerleading?

Whom should be used to refer to the object of a verb or preposition.

Jim is the one for whom the crowd is applauding.