What is a Jedi?
The Jedi began as a small group of people dedicated to philosophical study and practical realization of what is now known as "the Force." Founded in approximately 100,000 B.G.E (Before the Galactic Empire) and even then considered an antiquated religious sect of ineffectual spiritual mysticism, the Jedi succeeded in reestablishing the validity of the ancient tenants, honing them, and bringing their light again to shine in the galaxy.
Though originally a purely philosophical group, they soon added a deadly martial aspect to their core disciplines as a result of their vow to use their knowledge and power for the protection and betterment of others.
Shunning conventional weapons, the Jedi revived the ancient arts of swordsmanship.
To keep pace with modern weapons, however, they magnetically charged their blades
and were thus able to deflect projectile pistols and the then-newly-created laser
blasters. These charged swords in time evolved into the hallmark Jedi Light Saber.
What is "The Force"? (Basic)
What is "The Force"? (Detailed)