The English language has thousands of words in it. Many of which can become confused. Whom vs who and lie vs lay are two excellent examples of this.
In order to fully understand using who/whom, one must also understand whether the word is being used as the subject of the verb or the verb’s object. Whom being the objective form, who being the subjective form. “Who is the best student in the class?” is the correct way to use who. “To whom are you referring?” is the correct way to use whom. The confusion between the two arises more in a question because the word order is reversed. If you are not sure which to use, use who.
Lie vs lay grammar is even more confusing to most. The word lay means to put or to place. “Lay the book on the table.” This sentence is telling someone to put the book on the table. Lie means to recline. It is an intransitive verb meaning it has no object. The action stays with the verb. An excellent example of this would be a nurse telling you to “lie back”. People become confused because the past tense of lie is spelled the same as the present tense of lay. “He went to lay in bed,” is a sentence in which the past tense of lie is used.