WHAT IS THE DIFFERENCE BETWEEN A CAKE AND A SPONGE

My answer is a sponge is a lot lighter than a cake . Mrs Beeton (Victorian era ) cookery writer agrees with me , but goes on to explain that true sponges contain no fat ( no butter /marg). Sponges are made with eggs that do contain a small amount of fat and sugar that are whipped together to form an emulsion with some flour folded in so as not to disturb the bubble structure . All other cakes contain added fats eg butter/ marg .