The Force is a metaphysical, binding, and ubiquitous power that holds enormous importance for both the Jedi and Sith orders. Known as the Way in ancient times, the Force was viewed in many different aspects, including, but not limited to, the Light side of the Force, the Dark side of the Force, the Unifying Force and the Living Force. The first two aspects are concerned with the moral compass of the Force, as manifested by the conduct and emotions of living creatures who were themselves part of the fabric of the Force. The light side of the Force, favored by the Jedi, is the facet aligned with compassion, selflessness, self-knowledge and enlightenment, healing, mercy and benevolence, while the dark side of the Force, favored by the Sith, is the element aligned with hatred, fear, covetousness, anger, aggression, jealousy and malevolence. The latter two aspects are more of a philosophy than a code of practice: The Unifying Force essentially embraced space and time in its entirety, while the Living Force dealt with the energy of living things.
Though the Force is thought to flow through every living thing, its power can only be harnessed by beings described as "Force-sensitive." This Force-sensitivity is correlated with, and sometimes attributed to, a high count of internal microorganisms called midi-chlorians that are found in a Force-sensitive's blood: the higher the count, the greater the being's potential Force ability, though there are some exceptions to this rule. Force-sensitive beings are able to tap into the Force to perform acts of great skill and agility as well as control and shape the world around them.
Light side of the ForceThe 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. However (unlike the Sith) 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 it's 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.
Dark side of the ForceThe Dark side of the Force takes a more aggressive stance, with most abilities including harsh attacks while leaving no mercy. Sith are most known for using dark side actions to get what they want and drive them further from the light with actions such as harming, killing and murdering needlessly. Non Force-users also perform these actions, but because they have no atunement to the Force, their actions don't cause them to fall to the dark side.
Going along with the darkness associated with their side, Sith are known to shroud themselves in darkness and wield lightsabers of menacing color and complexity. Some Sith even use weapons that show different ways to inflict death and pain, but are mostly used for intimidation factors then actual combat use.