Just as "sugar" is a general term for a wide variety of ingredients that lend our baked goods texture and sweetness, "cake" or even "sponge" can have a multitude of meanings when you drill down and get specific.

And how the "biscuit" conundrum makes our heads ache! Generally, we rely on context to know if someone is referring to the French sponge or the English crunchy snacking item (a "cookie" for Americans) if we don't have the luxury of hearing the word pronounced. 

Some common sponges include:

• Genoise
   - whole eggs, sucrose, flour, and melted butter create this sturdy but light classic cake.
   
• Joconde
   - plays a major role in Opera, though it's no more of a diva than any of the other sponges listed here. Made from whole eggs, almond flour, confectioner's sugar, flour, and melted butter.
   
• Pain de Genes
  - the distinguishing ingredient here is almond paste, which gives this sponge a rich flavor and dense texture. 
   
• Dacquoise
   - a light and simple layer that is great as a base for tarts or small desserts. Made up of just egg whites, confectioner's sugar, nut flour, and sucrose, dacquoise is gluten-free. Because of its lack of flour, it can technically also be categorized as a meringue.
   
• Biscuit
   - here the whites and yolks (sometimes combined with whole eggs) are whipped separately with sugar and combined with butter and flour. A truly versatile layer for entremets.