According to Nigella Lawson, cake flour is mostly found in the USA. It is a low protein flour, between 6 and 8% protein, that has been milled very finely and bleached. Cake bakers have historically wanted a very white flour to make very white cakes.
Higher protein levels would make cakes tough rather than tender. While this flour makes light and airy cakes, it is generally not good for making breads., The low protein levels means there isn't going to be much gluten development, which in turn means little rise.