In Greek mythology, an Oread or Orestiad is a mountain nymph. Oreads differ from each other according to their dwelling: the Idaeae were from Mount Ida, Peliades from Mount Pelion, etc. Myths associated the Oreads with Artemis, since the goddess, when she went out hunting, preferred mountains and rocky precipices.
Les Oréades (1902) by William-Adolphe Bouguereau, in Musée d'Orsay
A nymph is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature, are typically tied to a specific place or landform, and are usually depicted as maidens. They were immortal like other goddesses, except for the Hamadryads, whose lives were bound to a specific tree.
Nymph
In this 1896 painting of Hylas and the Nymphs by John William Waterhouse, Hylas is abducted by the Naiads, i.e. fresh water nymphs
The statue of a sleeping nymph in a grotto at Stourhead gardens, England.
Hylas and nymphs from a mosaic in Roman Gaul (3rd century)