Strudel dough is a dry, elastic dough that is made to be rolled out very thin and stretched. It is a single piece of dough whereas puff pastry consists of lots of individual sheets. Hence some refer to puff pastry dough also as puff pastry sheets. Strudel dough contains almost no butter to make it more elastic whereas puff pastry needs grease in order to develop its characteristic buttery flavour.  Filo (or phyllo) dough in contrast to puff pastry dough is made with oil rather than butter. They are lots of thin sheets of dough that are laid on top of each other.