מה ההבדל בין whose ל whom?

whose שזה של משהו של בן אדם
who בן אדם

who' is a subject pronoun like 'he', 'she' and 'they'. we use 'who' to ask which person did an action or which person is in a certain state.
who wrote that letter?
who is the manager?
who is going to prepare dinner?

'whom' is an object pronoun like 'him', 'her' and 'us'. we use whom to ask which person received an action.
whom are you going to ask to the party?
whom did they choose as team captain?
whom did they summon?

'whose' is a possessive pronoun like 'his', and 'our'. we use 'whose' to find out which person something belongs to.
whose phone is this?
whose is this umbrella?
whose car is blocking the drive?