Esperides were in the Greek mythology the Nymphs of evening and sunset, and therefore also called the Nymphs of the West.
They lived in a marvelous garden somewhere in the Western world (of course somewhere west of Greece). In this garden there was a tree producing golden apples, that gave immortality when eaten.
Paris offered a golden apple to Helen of Troy, as a winner in a beauty contest, and thus began the famous war of Troy, that was immortalized by Homer. To protect the golden apples there was also a dragon, that was killed by Heracles.
In some old tale the Esperides garden was said to be located in Sicily.