This law states that everything has a male and a female component. This explains the concept of sex, in the simplest way possible! However, what we are actually talking about here are two specific energetic forces. There are only two, because they also adhere to the Laws of Polarity & Relativity.
The male energy flows outward and is considered to be positive, because it pushes outside of itself. Likewise, the female energy flows inward and is considered to be negative, because the energy is pulled inside of itself.