Peel, also known as rind or skin, is the outer protective layer of a fruit or vegetable which could be peeled off. The rind is usually the botanical exocarp, but the term exocarp does also include the hard cases of nuts, which are not named peels since they are not peeled off by hand or peeler, but rather shells because of their hardiness.
A fruit with a thick peel, such as a citrus fruit, is called a hesperidium. In hesperidiums, the inner layer (also called albedo or, among non-botanists, pith) is peeled off together with the outer layer (also called zest), and together they are called the peel. The zest and albedo, respectively, are the exocarp and the mesocarp. The juicy layer inside the peel (containing the seeds) is the endocarp.