Force Probability is the chance that a certain species of randomly attaining force sensitivity
The Force is a mystical energy field that gives many powers to those few beings that can use it. Those strong in the Force have an unusually high amount of a microscopic life form known as midi-chlorians. Midi-chlorians are not the Force but are merely an avenue for one to get in touch with it and to become one with it.
"Well, the force is what gives a Jedi his power. It's an energy field created by all living things. It surrounds us and penetrates us. It binds the galaxy together." - Ben Kenobi, A New Hope
"Life creates it, makes it grow. It's energy surrounds us and binds us." - Yoda, The Empire Strikes Back
"It's like engine tape. It's dark on one side, light on the other, and binds the galaxy together." - Unknown Starfighter Mechanic
The Force exists in all living things, although only a limited number of individuals have the ability to tap into and harness its power. When your character is created, depending on its Force probability, the server will secretly determine whether your character is Force-sensitive. No one will be told whether they are Force sensitive. This must be discovered through game play. If your character isn't born Force-sensitive, it might become Force-sensitive as it rises in Experience Levels (see Experience under Life and Death). Only Force-sensitive characters are able to train in, control, and master the Force.
Every being in the galaxy has some connection to the Force, however small it may be. As such, when they commit certain acts it changes how the Force reacts to them. Certain individuals are so evil that it almost seems as if the Force wants to reject them, and they leave a dark "taint" wherever they go, of varying strength. Most people remain completely unaware of this connection, this "measure" of their place in the Force. Only those who have become awakened to being able to use the Force seem to be able to read the status of themselves and others. This is the Force Meter.
All characters have a Force Meter that starts off at 0 representing complete neutrality. A character's light/dark 'meter' is a sliding scale from -50 (evil) to +50 (good). It is easier for a Force Meter to go down than up, so a good act will have a lesser effect than an evil one. Many people in the galaxy will find that their Force Meter has no practical effect on their daily lives, but remember that it affects how a Force User might deal with you, and if you ever want to become a Jedi, your past actions will affect your Force Meter right from the moment you are awakened to your Force abilities.
Rules about changes to the Force Meter can be found in the relevant sections of the Rules, especially combat. Special rules about Force Users and the Force Meter can be found in the section on the Force.