See also: Philosophy
The Force is an energy field generated by all living things. It surrounds and penetrates everything, binding the galaxy together. There are two sides to The Force. Peace, serenity, and knowledge form The Light Side, while The Dark Side consists of aggression, anger, and fear. The universe is a place of balance: life and death, creation and destruction, love and hate. As such, both sides of The Force are part of the natural order.
Some beings are more attuned to The Force than others. Whether they understand it or not, they can feel The Force flowing through them. Of those that are sensitive to The Force, beings that study its ways can learn to manipulate its energy. The Jedi fall into this category, using their knowledge of The Force to give them their powers. But theirs is not the only Force-using tradition.
The Sith, The Witches of Dathomir, and others embrace The Dark Side of The Force, while a variety of alien cultures, such as Ewok shamans and Ithorian eco-priests, call The Light Side of The Force by different names. Understanding of The Force manifests in many ways.