Lemon , rind, juice and peel are used in a wide variety of foods and drinks.The whole lemon is used to make lemon liquer, lemon curd or marmalade.Lemon slices and lemon rind are used as a garnish for food and drinks. Lemon zest, the grated outer rind of the fruit, is used to add flavor to baked goods, puddings, rice, and other dishes.

The Juice
Lemon juice is used to make soft drinks, lemonade and cocktails. It is used in marinades for fish, where its acid neutralizes amines in fish by converting them into nonvolatile ammonium salts.
The Peel
The salt penetrates the peel and rind, softening them, and curing them so that they last almost indefinitely. The preserved lemon is used in a wide variety of dishes. Preserved lemons can also be found in Sicilian, Italian, Greek, and French dishes.
The Oil
Lemon oil is extracted from oil-containing cells in the skin. A machine breaks up the cells, and uses a water spray to flush off the oil. The oil/water mixture is then filtered and separated by centrifugation.
Leaves
The leaves of the lemon tree are used to make a tea and for preparing cooked meats and seafoods.
Source: en.wikipedia.org