(Single Lightsaber)
Lightsabers are an iconic weapon used by Jedi. This is an elegant weapon, for a more civilized age. Lightsabers began their history as energy swords, wielded by the Jedi Knights millennia ago in the beginning days of the Jedi Order. The blade has always served as an instrument of peace, not war. As such, a Jedi is to only defend themselves with their saber and never needlessly harm another being.
(Double Bladed Lightsaber)
Double Bladed lightsabers are seen as strictly offensive in nature. It's double blades allow for more ways to attack. It also increases the defense of a Jedi, allowing them to strike at a enemy, while blocking an incoming attack. They are reserved for those Jedi who are strong enough to resist the lure of violent actions, such as Temple Guards and Advanced Jedi Knights.
(Dual Bladed Lightsaber)
Dual-wielding sabers is not uncommon in the Order, and is not viewed as a wholly offensive act. The reason for this is the existence of a shorter lightsaber in the off-hand, known as a shoto saber. The purpose of this small blade is to allow for quick parries and defensive actions without compromising the main lightsaber blade. There are occasions where both blades are the same length. The style of combat remains relatively similar to its shorter more common version.