Ogres are said to be able to change their shape at will into animals or objects, and they often dwell in marvellous palaces or castles, sometimes underground.
In Scandinavian countries ogres are sometimes associated with trolls; they are considered to be masters of castles built in the mountains, keeping fabulous treasures (compare with the Irish leprechaun); this creature is considered to be either a giant (most commonly) or a dwarf.
In art, ogres are depicted with a big head, abundant and hirsute hair and beard, a huge belly, and a strong body.
Literature for children has plenty of tales mentioning ogres and kidnapped princesses who were rescued by valiant knights and, sometimes, peasants. Ogres are also popular in fantasy games and movies.
By extension, the term ogre applies to disgusting persons with a violent temper.
O.G.R.E is also a Steve Jackson Games game involving very large tanks.