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.
Depending on the thickness and taste, fruit peel is sometimes eaten as part of the fruit, such as with apples. In some cases the peel is unpleasant or inedible, in which case it is removed and discarded, such as with bananas or grapefruits.
The peel of citrus fruits is bitter and generally not eaten raw, but may be used in cooking, e.g. chenpi. The outermost, colored part of the peel is called the zest, which can be scraped off and used for its tangy flavor. The fleshy white part of the peel, bitter when raw in most species, is used as succade or is prepared with sugar to make marmalade or fruit soup.