A wheat flour typically milled in Italy, where millers grade their flour by using a ‘zero’ rating. A single zero flour is quite coarse in texture, like very powdery semolina, whereas triple zero is much finer like cornstarch. But everyday flour is usually classed as double zero, or ‘00’.
Beyond that, millers will then combine different wheat varieties to make flour to suit different purposes. So you can buy a ‘00’ flour suitable for pasta with a very golden colour, and a ‘00’ flour suitable for plain white bread. Look on the packet and see what use is suggested to get the best result. In cake recipes it can be replaced with plain flour; in bread, pizza and pasta recipes it can be replaced with strong white bread flour. It is often lower in protein than British flours and so produces a much crisper crust in bread, and a finer texture in cakes.