What is a virtuosi piece?
Just looking on competitions repertoire,
I find "things" that are call :virtuosi pieces.
What are these?
Is it all Paganini pieces or is it tchaik. and sib. concerto?
Waiting for answers for this question(which may be extremely stupid)
Your question is sort of unclear and challenging to understand. However virtuoso pieces are typically short of long and not concerti. Short think: Sarasate dances, Kreisler short works, wienawski short works, Paganini caprices, Ernst. Maybe for longer works: pagganinia, Carmen fantasy (Sarasate And waxman.) nel cor piu, Wieniawski theme and variations.
I would agree with Mark. Typically showy offy type pieces as mentioned above
Yeah, that's what competitions/schools mean when they say virtuoso piece.
Also don't forget Ravel Tzigane, Saint-Saens' Havanaise and Introduction and Rondo Capriciosso!
The following list contains quite a few of them, but there are still many others, e.g., Bazzini "Dance of the Goblins" is not on it:
It was Bazzini. (Carlo Rizzi's last words. Sort of.)