The Pentagram in the magickal sense represents the ability to draw or direct magic into the material world we live in. It is a symbol of Earthly exsistance (4)...connecting to higher (or lower) "supernatural" forces (+1). The Five points of the Pentagram represent the Arms, Legs, and Head of a human, which is the highest achievement of the material world. The Four points where the Arms and Legs touch symbolize the Earthly world, with its four compass points, four seasons etc.
The 'Upright' Pentagram with the Point/Human Head at the top represents the desire or ability to connect with the "Higher Forces" or powers of "Light", in the spiritual/metaphysical realm and focus them into the material/earthly world around us...Knowledge, understanding, wisdom, love, honor, humility etc...as well as the souls desire to progress upward in it's spiritual development.
The 'Inverted' Pentagram with the Point/Human Head at the bottom represents the desire or ability to draw the "Lower Forces" or powers of "Darkness" into our earthly world...Ignorance, selfishness, arrogance, lies, deciet, harm and death etc...the soul has been abandoned in exchange for worldly desires. It is commonly used as a symbol of Satanism.
The difference between Pentagrams and Pentacles...
The Pentacle is believed to have originated with the Kabalistic magick of King Solomon (about 900B.C.). With few exceptions they are circular with geometric designs of various shapes that are usually associated with the sigils of the Angels and/or Demons. They may be engraved on a metal disk or written on parchment paper and they are used to summon and influence the spirits. Historically it is known that Pentacles were used for magical purposes long before Pentagrams. However, Pentagram designs have been found that are older than known Pentacles...but it is not known if they were considered religious or magical symbols.
The Pentagram is the star shaped pattern described above, upright or inverted. When set in a circle or on a circular disk it is sometimes called a Pentacle. The Pentagram is known to have been associated with magick from the middle ages in European Paganism. Historically, where magick is concerned, the Pentagram was probably a Pagan adoption of the Pentacles brought with the Jews and later Christians as they spread across Pagan Europe. The second Pentacle of Venus from the Key of Solomon has what is commonly called a Pentagram on it but it is used and understood differently by the Kabbalists, than the Pentagram of the Pagans. The Pagan mystics and witches of Europe did not understand the Hebrew language or Kabbalist magick but were aware of the powers associated with the Pentacles and the magical symbology ssociated with the Pentagram. Thus they adopted the Pentagram as a powerful symbol of Pagan Magick.