It is a Wiccan thing, it has been adopted by Wiccans, they weren't the first to use the pentagram in either form. But we will never know who truly was the first or the first esoteric meaning. Someone charted the orbit of Venus and saw a pentagram, who knows if they added an interpretation.
I have seen the inverted pentagram used in two ways in my personal work:
1) As a way of invoking force down into the vicinity and the sphere of sensation in a forceful manner rather than the balancing manner which is common in most rituals.
2) As a way of establishing/realising the essence of spirit present within matter and the material world rather than presupposing the spiritual and the material are not one.
No symbol is good or bad, it all matters how it is used, one's understanding of the symbol, and within magic, one's tradition. Some people gain personal symbol meanings through personal work. Others, as is the case with Wiccans, gain an understanding of symbolism through initiation into a system.
A symbol is just a focal point, an external referent for a practitioners Will, or as a method of charting and containing esoteric knowledge. Both normally intersect.
Does it mean Satan? Yes, to some people, no to others. The symbol itself is nothing more than the orbital path of venus portrayed in a less popular way. Anything relating to the occult or magic which is attached to the pentagram is pertintent to whatever tradition one follows, thus the meanings vary from person to person.