"whom" is the objective form of "who." "To whom am I speaking" "whose" is the possessive form of "who." "Whose shoes are these?"

Whose? Mine/Yours/His/Hers/Ours/Theirs. Whom? Me/You/Him/Her/Us/Them.

Although it is technically correct English to say "whom" it is never said in everyday language because it sounds so old fashioned. E.g. "To whom am I speaking?" becomes "Who am I speaking to?". I think we're supposed to use "whom" when it's the dative case but I don't know when the dative case occurs as I've never been taught, sorry! But hope that makes you less worried about using "whom", if it's "real life" then you will never use it but in an exam you might have to.