The Force is a universal energy force that binds all life together. Over a millennia, sentient beings learned how to harness the Force to use as a tool and as a form of supernatural sense. Many sects have arisen with the goal of utilizing the Force and studying its abilities, often with different intentions in mind and often dedicated primarily to either the Light or the Dark Side. The most famous and influential of these sects are the Jedi Order and the Sith, who have been at odds since their creation.
Within the Force, there is the Light Side and the Dark Side, as well as other philosophical views of the Force.
The Light Side
The Light Side of the Force, primarily represented by the Jedi, is a selfless ideal. Followers of the Light are often willing to sacrifice themselves in order to save somebody else. They believe in peace and harmony with one another and finding balance in the Force. Using powers of the Light Side requires peace and calm thoughts, giving of themselves and attempting to find peaceful resolutions. They believe in following the will of the Force, viewing themselves as a tool to be used by the Force.
The Dark Side
Followers of the Dark Side, primarily represented by the Sith, are often selfish. They believe in the survival of the fittest. Their primary goal is to acquire power and control, conquering those weaker than them. They feed on their own hatred and the hatred of others. Using powers of the Dark Side requires taking from others, causing pain, and feeding on their own dark emotions. They believe in controlling the Force; they deny the existence of fate and believe they can create their own destiny.