In the Star Wars series, a Jedi is a Force-user aligned with the light side. The Force is a life-force that binds the universe together and may be used to change events in the world at large, by manipulating the underlying nature of life. In Star Wars, the great power that this entails has divided Force-users diametrically: those who favor its use for good align with the Light, while those that seek to use their force powers for personal gain, inevitably are tempted by this slight variance to fall utterly to the Dark side. To walk in the Light, as a Jedi, is a strict way of life, and so is a challenge for those in the Star Wars universe to live up to. As such, the Jedi, at least in the Prequel Trilogy, were shown to take children in at a very early age to train them in ways of the Jedi, and their code included no attachments.
Jedi use "lightsabers," or swords emitting beams of pure light, to deflect energy weapon fire and as an offensive weapon. The lightsaber is a symbol of peace and refinement, according to Obi-Wan Kenobi, less casual and haphazard than traditional weapons, and implying a commitment to the finesse and perfection of form required by duelists and light Jedi alike. The prequel trilogy also implied that they used midichlorians to decide someone's potential.
George Lucas has stated that he came up with the idea of "The Force" as he wanted to promote a vague idea of hollow Hollywood-style spirituality without referencing any recognizable religion. Despite this, the depiction of the philosophy and beliefs of the Jedi, including the insinuation that an adherent to the Jedi way is required to maintain "balance" regarding their force usage, as well as several of Yoda's statements and the disallowing of any attachments, including love and promoting letting someone die, as well as Obi-Wan implying twice that the Jedi adhered to moral relativism, seem to be a way to promote eastern mysticism (in particular Buddhism) and undermine Christianity in the movie's western audience. This is typical of the New Age movement's tendency to use parts of different religions willy-nilly without any structure of sense, and overall was a further demonstration of the film being influenced by Lucas' growing up in 1960's California, which he had briefly referenced in an interview regarding his film Red Tails.
In addition, when commenting on Anakin Skywalker's fall on the onset of Attack of the Clones' release, Lucas said "He [Anakin Skywalker] turns into Darth Vader because he gets attached to things, he can't let go of his mother; he can't let go of his girlfriend. He can't let go of things. It makes you greedy. And when you're greedy, you are on the path to the dark side, because you fear you're going to lose things, that you're not going to have the power you need."
Effects on the Real World
The Jedi Way is a fictional religion/philosophy from the Star Wars movie series. In a recent census in Australia, pranksters claimed "Jedi" as their religion in hope of getting it recognized as a legitimate faith.