Why is pentagram important to witches?

"It is a symbol which Solomon conceived once To betoken holy truth, by its intrinsic right, For it is a figure which has five points, And each line overlaps and is locked with another And it is endless everywhere, and the English call it, In all the land, I hear, the Endless Knot." Poem of Sir Gawain and the Green Knight

An ancient five-sided star

A pentagram, a five-sided star, constructed by intersected five straight lines, is one of the oldest markings known to humanity. It is a symbol fraught with mystery, intrigue, and meaning. It is also called a pentacle or Pentalpha, and gets its name from the Greek penta, meaning “five” and gramma, meaning “a letter”.

The pentagram was apparently discovered by astronomical research in the Tigris-Euphrates region of the Middle East, as far back as 6000 B.C.E. Mesopot