Since you ask out of curiosity, I'd be happy to explain. You're certainly not the first person to ask me about this and not likely to be the last.
First, the "pentagram" is a simple five-pointed star, nothing more. It's the same one we all learned to draw as a child and the same one we see on the American flag and carried by many police officers as badges. When a circle is placed around this star, it becomes the "Pentacle," the primary religious icon for most Pagan paths (yes, there are many various Pagan paths).
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The pentacle represents the 5 elements that make up all things in our world: Earth, Air, Fire, Water, and Spirit. We have all of these within us and without them, life could not exist. The point of the star facing straight up represents spirit, or that spark of the Divine that we all carry. By placing this point above the others (material elements), we concede that the divine rules over the Earth.
Just as Satanic groups use the reversed cross, they also use the Baphomet, or reversed pentacle (often with a goathead on it). By placing the spirit point down, they are claiming that humans are greater than the Divine. As I don't practice this, or know anyone who does, I cannot intelligently speak any more than that on Satanism, but that's their connection to the pentacle.
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