The light side of the Force, often simply refered to as the Force, used by the Jedi Order in particular, was the side of the Force aligned with honesty, compassion, mercy, healing, self-sacrifice, and other positive emotions.
The light side of the force takes a more defensive approach to combat, as some of the abilities channeled by Jedi include protecting themselves or others with force shields, healing themselves or others without resorting to stealing life from their opponent (unlike the Sith). However, Jedi are still a force to be reckoned with on the battlefield, and an experienced and battle-hardened Jedi can be difficult to take down in battle.
Jedi are the most common wielders of the light side of the force. Visually, the light side of the force generally appears as lighter colours than its counterpart, the dark side of the Force, such as blue or other light colours.
Naturally, the Light side is the counterpart of the Dark Side, which focuses on self-serving and anger-fuelled powers, the light side is also very capable at defusing such dangerous situations.