What is Relax?

Relax — In pastry-making, this means to set aside the pastry in a cool place after rolling to allow the gluten to contract (because it will have expanded during rolling). This reduces the danger of the pastry shrinking in the oven. It's also a term used to refer to batter mixes - meaning to set the batter aside to allow the starch cells to swell, which will give a lighter result when it's cooked.