00 flour is the most refined soft wheat flour: white and very fine, made almost entirely from the inner part of the grain. It is the most widely used in pastry and egg pasta, because it makes smooth, elastic doughs.
I often use it together with other flours, such as rice, wholemeal, spelt or buckwheat: 00 gives structure and lightness, the others flavour and nutrients. It is the way to make shortcrust pastry and bread that are easy to work but have more character.