A five pointed star is not necessarily made with five lines/strokes. Some may have only the outermost lines drawn. Whereas a pentagram has five solid, unbroken lines. Examples of a five pointed star are the fifty on the USA flag. Solid white, no lines seen. Just the border of colors (white and blue in this case).
https://en.wikipedia.org/wiki/Pentagram
https://en.wikipedia.org/wiki/Five-pointed_star
Pentagrams also have been associated with various religious beliefs (Christian, Wiccan, Baha'i, Later Day Saints/Mormon, among others) . In Christian beliefs it symbolizes the "five wounds of Christ"
Also, the Pentagram has some connections to the "Five Elements" in Chinese Tradition (fire, earth, water, metal, wood)
Also, the occult has its uses for this symbol. The West African Serer religion use it, (symbolically, its the star Sirius). The Druze use it in a multicolored fashion. It also appears on the flags of Morocco and Ethiopia. The Order of the Eastern Star (associated with the Freemasons) also use it. Also, astronomers have tracked the orbit of Venus (as seen from Earth) and called it the Pentagram of Venus.
Short version - The Pentagram and the Five pointed star, though similar, are quite different. One is 'merely' a shape, and the other, while also a shape, has world wide religious symbolism as well as other associations/uses.
