A chiffon cake is a very light cake made with vegetable oil, eggs, sugar, flour, baking powder, and flavorings. It is a combination of both butter and foam type (sponge type) cakes.
The purpose of the fat is to help the texture and the tenderness and keeping quality of the cakes. Some fats that go into a chiffon cake would be a large quantity of eggs or oil.
The purpose of the eggs is to help the cake improve the color and the texture of the cake. You would need 7 eggs and you would have to separate them into egg yolks and egg whites.
The purpose of the leaving in the chiffon cake is to help the cake rise when it is baking in the oven because without it you would probably have a flat cake. In the chiffon cake would be baking powder or baking soda.