Puff pastry is a light, flaky pastry dough that contains several layers of dough with fat, usually butter, between each layer. The butter gives the pastry a rich taste. The dough is rolled out and fat or butter applied on the dough. The dough is folded together, let set for a few minutes at a cool temperature, and rolled out again. Again butter is applied on the dough and the process repeats.
The butter layers between the dough layers cause the pastry to rise because when the butter is heated, it creates steam, causing the dough layers to lift up. As the dough cooks, it hardens and creats the crunchy layers of dough.
Frozen puff pastry can be found at most grocery story in the frozen food section near the pies.
Puff pastry is used in my German Apple Strudel Recipe.