Who - refers to a person
ex. Who are you ?
Who is that girl ?
Whose - refers to a stuff/thing belonging to a person .
ex. Whose ballpen is this ?
Whose wallet is this ?
Which - What, of those mentioned or implied .
ex. Which one is bigger ?
Which one is better ?
Whom - What person or people; which person or people, as the object of a verb.
ex. Whom did you ask ?
To whom it may corncern.
That - an object/person that you are pointing to ; an object or person far from you .
ex. What is that ?
Is that Jenny ?
