Lime is calcium oxide. Quicklime is anhydrous calcium oxide.Slake lime is calcium hydroxide--add water to calcium oxide and it turns into calcium hydroxide.
In the Florida Keys, Key Lime pie is a famous dessert. Limes are also garnishes for a variety of cocktails.
Limes are a naturally growing fruit, and are not "made out of" anything.
calcium, the chemical element with the symbol Ca and atomic number 20