Croissant, danish and puff pastry doughs are all laminated (layered) doughs, created through turning. 

Laminating is accomplished in croissant and danish doughs by encasing a 3/4" x 12" x 14" block of butter in dough creating 3 layers, 2 of dough and 1 of butter. This is then rolled out and folded several times creating a total of 81 alternating layers of butter and dough. 

Laminating is accomplished in biscuit recipes simply by making turns.

The key to success in this process is maintaining the integrity of each layer. If the lamination is successful and the layers are maintained the product will be light and flaky.

The leavening in laminated doughs is derived mainly from the steam generated by the moisture in the butter during baking. As the steam expands in the oven it lifts and separates the individual layers. While croissant and danish doughs do contain a small amount of yeast to aid in leavening, puff pastry relies solely on steam and requires a higher percentage of butter and a more elaborate folding process that creates nearly 800 layers.

There are other factors that affect the success of the lamination. The dough must have a well-developed gluten structure to be able to support the expansion in the oven. The fat must be rolled evenly in continuous layers. To accomplish this the butter must be in a "plastic" state when laminating. That is, able to be rolled out easily without breaking into pieces (not too cold) but firm enough that it won't squeeze out of the edges of the dough layers or allow moisture to seep into the dough (not too warm). The butter and dough should be at approximately the same temperature, and the layers of each must remain distinct from each other or the product will resemble brioche more than delicately layered and flaky laminated dough.