Puff pastry, also known as pâte feuilletée, is a flaky light pastry made from a laminated dough composed of dough (détrempe) and butter or other solid fat (beurrage). The butter is put inside the dough (or vice versa), making a paton that is repeatedly folded and rolled out before baking. The gaps that form between the layers left by the fat melting are pushed (leavened) by the water turning into steam during the baking process.
Since the process of making puff pastry is generally laborious and time-intensive, faster recipes are fairly common: known as "blitz", "rough puff", or "flaky pastry". Many of these recipes combine the butter into the détrempe rather than adding it in the folding process and are thus similar to a folded short crust.