It is an Italian ritual: dip a piece of bread in the last layer of sauce left on the plate. Is doing it polite or not? Ladies and gentlemen, let's do "Scarpetta"!
If you are in Italy, when you finish your pasta, you don't throw away the last layer of sauce. "Fare la Scarpetta" means to use a piece of bread to collect the last drops of sauce on your plate (holding the piece of bread strictly by hand).