Pentagram
The pentagram is a five-pointed star, geometric symbol with millennial history: present in Sumer (3000 BC), Pythagorean (Greece), Christian (5 wounds of Christ), Wiccan and Satanic. Pointed up = harmony, spirit above matter; pointed down (inverted) = matter above spirit, popularly satanic.
Wicca and Satanism
The Wiccan pentagram (pointed up, in circle) symbolizes the 5 elements (4 + spirit). The inverted pentagram, popularized as satanic by Anton LaVey (Church of Satan, 1966), was originally a positive Pythagorean symbol.