The Pentacle Symbol

In it's modern use, the Pentacle (or Pentagram) is an interwoven five pointed star with each point symbolizing one of the five spiritual elements; Earth, Air, Fire, Water and Spirit. It is often called the 'Star of Knowledge' and is a powerful meditative symbol, helpful in understanding one's connection to the Universe or the 'All', as in the 'Oneness of all Things'.
A pentacle is used in some neo-pagan magical traditions, such as Wicca, alongside other magical tools, most often a protective talisman or amulet used in magick and ritual as a focus of energy. It is generally placed on an altar or worn around the neck.

Today, the words pentacle and pentagram are generally synonymous, according to the Online Oxford English Dictionary, tracing the etymology through both French and Italian to Latin, noting that, in Middle French language, the word "pentacle" was used to refer to any talisman. In many tarot decks and in some forms of modern Paganism and witchcraft, pentacles often prominently incorporate a pentagram in their design.

The pentacle, (five pointed star or pentagram) seems to have originated as the symbol of a Goddess who was worshiped over a large area extending from the British Isles to Egypt and even beyond. This Goddess is known by many names, including Kore, Car, Cara, Carnac, Ceres, Core, Kar, Karnak, Kaur, Kauri, Ker, Kerma, Kher, Kore, Q're, etc.. In Rome, known as Carmenta and Ceres and was said to have created the Roman alphabet. Many English words have evolved from her name Ceres, such as cardiac, carnal, cereal, core, corn, and kernel. These give some clue to Her many aspects.

The apple is the sacred fruit of Kore's. When you cut an apple through its equator, the seeds form the shape of a pentagram, Many modern Pagans and Wiccans cut apples in this manner as a part of meditative ritual practice. The pentacle is the most common symbol in Wicca.

In Celtic Paganism the pentacle is sometimes the symbol of the Morrigan (Morgan, Morgana), Goddess of the Underworld. Five is a sacred number in Celtic Paganism as is evidenced from the old saying in Ireland; "Ireland had five great roads, five provinces and five paths of the law. The fairy folk counted by fives, and the mythological figures wore five fold cloaks."

The pentagram was used in ancient Greece, most notably by followers of Pythagoras (586 - 506 BCE) who, after establishing his school to pursue knowledge in mathematics, music, religion, and other areas, was driven underground. His followers, the Pythagoreans used the pentagram as a secret symbol to identify themselves to one another.
Many followers of darker or more destructive spiritual purposes have used the inverted pentagram as a sign of turning light into dark or good into bad, or even in putting earthly material over spirituality.
That's not to say an inverted pentagram is always bad or negative, as it's also used in some traditions to symbolize a practitioner who is newer in their development. Stemming from a Masonic symbol, The Medal of Honor for all branches of the U.S. Military uses an inverted pentagram and even Washington D.C. streets make a perfectly symmetrical inverted pentagram, the White House is located at the tip of the lower arm.

In it's long history, the pentacle has meant many things to many people. It seems to have been used as a positive symbol far more than a negative one.