The Force

The Force is what gives a Force-Sensitive his or her's abilities. There are four aspects of the force but only two of them appear in Star Wars: The Force Unleashed (the Dark Side and Light Sides of the Force).

Dark Side
The dark side is a very tempting aspect of the Force. At the beginning of Star Wars: The Force Unleashed, Marek is a dark side practioner. You can tell this by the use of force choke by Marek at one point, a renown dark force ability and his willingness to kill all that he sees.

Light Side
The light side is the less tempting aspect of the Force. After Darth Vader "betrays" Marek he starts using the lighter apects of the force. An example of a light side ability is the Jedi Mind Trick.