The way it was explained to me is that there is a difference between pressing and ironing. When you press, you do one section and then lift up the iron and put it down on the next section. You don't slide the iron like you do with ironing. That way you don't stretch your fabric. She said that is why it is called pressing. You place your iron, press down, lift and place your iron on the next section, press down and so on. I hope that helps and doesn't confuse you. I always press as I go because it gives you a crisper seem to work with and is just so much easier than a seem that is not pressed. Also, it helps your seems and corners come together better.