Lemon peel is the thin, yellow outer covering of the lemon, which is typically used in cooking and baking to provide characteristic lemon aroma and flavor to dishes without the acidity and extra liquid adding lemon juice would involve. Commercially, lemon peel is mechanically processed to make lemon oil -- there are small glands in the peel that rupture, releasing the oil.
The aroma of lemon peel is sharp and fresh, with a strong, waxy-lemon-floral aroma, which is mainly limonene, beta-pinene, and gamma-terpinene, with neral and geranial also contributing some scent. In cocktail usage, lemon peel can either be muddled in the bottom of the tin to release oils, or used as a garnish to provide lemon aroma with each sip.
Lemon peel can be cut into small matchsticks or removed from the lemon with a citrus zester to make lemon zest.