It depends on the path but most view it as a protection symbol and a representation of the five main elements. Starting at the top and going clockwise top point is spirit, second is air, bottom right is fire, bottom left water, then earth and back to spirit. Of course some view things like metal, wood, and chaos as elements, but those are the most commonplace.
Also note the pentacle and pentagram are different. One has a circle, the other does not.