The Dark side
Characters who are Sith Lords such as Darth Vader have special dark force powers. They can interaction with Dark Lego® objects. And they can use The Force on certain characters to hurt them instead.
The Light side
The light side of The Force prefers a more peaceful, non-aggressive way to handle situations. Jedi characters can use The Force on certain characters to confuse them or move them.
The Force can be used to gain more studs (money). Every time you use the force on something new, you get awarded with studs. There are also destructible Force objects, like a radio, when destroyed these items will generate studs. Sometimes, using The Force will help you find minikits, power bricks, or even for fun (The more creative players will find these)