Whose is an interrogative words.  It's used to ask all the relationships. For example: whose is that shirt? That is Tim's or  That is mine. correct?

Whose can also be used as predicative in a sentence. For example :  This coat is her, not yours.   yours is as predicative in this sentence.  correct ?

When all relations refer to something or something, the noun behind whose can be omitted. For example: Whose is that book?  That is Tim's book.= That is Tim's.  correct?