No, they are all laminated dough, meaning they are all layers of flour and butter, and yet they are all different from each other. Puff pastry has no yeast and no eggs. Croissant dough has the addition of yeast and is made with milk just like bread, but with lamination. Danish pastry has yeast as well as eggs. While puff pastry goes thru 6 folds, a croissant goes thru just 3 or 4 folds, and a Danish pastry has about 3 turns as well.  Lastly, puff pastry has a flaky crusty quality, while croissant has a more bread-like quality and the Danish pastry has a chewier texture - Read more about the different types of pastry