Lamination
Lamination is the technique of folding and rolling dough around butter to build many alternating layers, which bake into flaky, lifted pastry.
Each fold multiplies the layers: three letter folds of a simple dough produce dozens of butter sheets. In the oven, water in the butter turns to steam and forces the layers apart.
Full puff pastry is the extreme case, with hundreds of layers. Rough puff cheats by leaving visible butter lumps in the dough and folding fewer times, trading some lift for speed.