Literally translated, the Greek word phyllo means "leaf." Culinarily, it refers to tissue-thin layers of pastry dough used in various Greek and Near Eastern sweet and savory preparations, the best known being spanakopita. Phyllo (also spelled filo) is very similar to strudel dough. Packaged fresh and frozen phyllo dough is readily available the former in Greek markets, the latter in supermarkets. Unopened, phyllo can be stored in the refrigerator for up to a month. Once opened, use within two to three days. Frozen phyllo can be stored for up to one year. Thaw overnight in the refrigerator. Refreezing phyllo will make it brittle.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.