What are the difference of the "Pentagram" and the "Pentacle"?
Well the has been lots of confusion between these two almost similar magic(k)al symbols. Except for one thing. A Pentagram is a star with a circle around it. This I believe represents the circle of witchcraft. The star itself represents the 5 major elements; Spirit, Air, Water, Earth, and Fire (probably not in that order). I will show you a couple of picture of the difference between the two and the similarities as well. As for the Pentacle is a star by itself. Representing the individual star, representing the 5 elements.
What properties do they have in magic(k)?
The Pentagram is the most used symbol in the magic(k)al world. The Pentacle is the second most used symbol as well. These two have been used for "warding off" and "Capturing". There are many misinterpretations about the two symbols of magic(k), some people state the pentagram and pentacle are both the same, and represent the hail of Satan, which is not true, not everyone that caries a pentacle or pentagram hails the devil, or any other entity.
There is a sign of the Satanists, which is a upside down pentagram or pentacle. Remember not all Satanists are evil, there are some really friendly Satanists there are different kinds of Satanists.