Question

Many English speakers mix up ‘who’ and ‘whom’. Do you know which of these sentences is incorrect?

Answer 1

Yes both terms are different
→Who should be used to refer to the subject of a sentence. 
→Whom should be used to refer to the object of a verb or preposition.

for example consider this
Who would like to go on vacation
Whom do you believe?

Try substituting “he” or “she” and “him” or “her.”
If “he” or “she” fits, you should use who.
 If “him” or “her” fits, you should use whom.