The pentacle in wiccan represents many things. It can represent the 5 elements fire, air, water, earth as demon started on the elements page but it can also represent the goddess in her 5 forms and the god in his 5 forms.
The goddess in her 5 forms are Great Grandmother/wise woman her element is spirit/aether, Mother her element is water, Lover-Queen her element is fire, Grandmother her element is earth, Maiden her element is Air.
The god in his 5 forms are Lord of the Other world his element is spirit/aether, Husband and Young King his element is water, The Phallic God his element is fire, The old king: The sacrifice his element is Earth, The young God his element is Air.
The pentacle is usually worn around most witches necks as a symbol of the perfect human being. If a pentacle is upside down it is a sign of evil. Usually the upside down pentacle is worn by Satanists. It can also be worn as a degree in wiccan magik.