What is the difference between 'che' and 'cosa'? Is 'Cosa vuole?' also correct?
according to native italian speakers on various internet forums, you can use 'che cosa', 'cosa', and 'che' interchangeably, the latter 2 being abbreviations.
They are same, you can use also togheter "che cosa vuole?" Or "che vuole- cosa vuole"
Is it a polite question or does it sound rud, like the english what do you want?
Using "che" alone makes it rude, yes.
Rude: Che vuole?!
Neutral/rude depending on pronunciation: (Che) cosa vuole?(!)
Polite: cosa desidera?
Why is "What do you want?" not considered wrong here? Am I missing something or is it idiomatic?
The pronoun ending! I believe "vuole" is he/she/it, while you would be "vuoi".
Never mind, I see you said NOT considered wrong. Formal you, Lei, also uses the he/she/it verb ending, so I imagine that's why.