Amarna art was a new style of Egyptian art introduced under the rule of Akhenaton. Prior to his rule during the New Kingdom of Egypt, art was extremely stiff and stylized. The strict Egyptian caste system dominated by the preists, allowed art to be created only within certain guidelines for specific purposes. Most art was either political in nature -- depicting stolid rulers who were supposed to represent the solidity and placidity of Egypt -- or religious -- depicting the gods the way they had always been depicted.
Akhenaton's radical revision of the polytheistic Egyptian religion into a monotheistic belief centered around Aton-Ra allowed creativity in all forms of art. Amarna art is the result of that creativity. It is light and naturalistic. Although the figures represented are idealised (look better than they really were) they are no longer exaggerated to make a political or religious point.
Perhaps the best example of Amarna art is the portrait bust of Akhenaton's
Queen, Nefertiti.