A Pentagram is a ancient symbol, used to keep something either in or out.
The Points on a Pentagram mean multiple things and these things are as follows: Earth, Air, Fire, Water, and Mind/Spirit depending on your preference. A Pentagram is not limited to keeping things in or out, and in fact can be used in multiple fashions as an altar, meditation space, and more. The pentagram is not evil in nature, but it is often portrayed in such a way. Pentagrams have many functions and one should keep an open mind when diving into such research of them. Take all knowledge with a grain of salt.