Green Lantern is the name of several heroes in DC Comics.
Green Lanterns from Earth
Alan Scott: A mystical "green flame" meteor fell to Earth in ancient China. The voice of the flame prophesied that it would act three times: once to bring death (a lamp-maker crafted the green metal of the meteor into a lamp; in fear and as punishment for what they thought sacrilege, the local villagers killed him, only to be destroyed by a sudden burst of the green flame), once to bring life (in modern times, the lamp came into the hands of a patient in a mental institution who fashioned the lamp into a modern lantern; the green flame restored him to sanity and gave him a new life), and once to bring power. By 1940, the lantern passed into the possession of Alan Scott, a young engineer. Following a railroad bridge collapse in which he was the only survivor, the flame instructed Scott how to fashion a ring from its metal, to give him fantastic powers as the superhero Green Lantern. He adopted a colorful costume and became a crimefighter. Alan was a founding member of the Justice Society of America.
After the Crisis on Infinite Earths, a Tales of the Green Lantern Corps story was published that brought Scott even closer to the Corps' ranks. It was revealed that Hal Jordan was predated as Earth's Green Lantern by a citizen of ancient China. Not only was the Corps' now-familiar green, black and white uniform motif not yet adopted, but this ancient Chinese GL altered the basic red of his uniform to more closely resemble the style worn by his countrymen. Power ultimately corrupted this early GL and the Guardians of the Universe allowed his ring to manifest a weakness to wood, the material from which most Chinese weapons of the time were fashioned. This allowed the locals to ultimately defeat their corrupted “champion." His ring and lantern were burned and it was during this process that the “intelligence” inhabiting the ring and the lantern, and linking them to the Guardians, was damaged.
Centuries later, it was explained, when Scott found the mystical lantern, it had no memory of its true origins, save a vague recollection of the uniform of its last master. This was the origin of Scott’s distinctive costume. Due to the damaged link to the Guardians, those immortals presumed the ring and lantern to be lost in whatever cataclysm overcame their last owner of record. Thus it was that Scott was never noticed by the Guardians and went on to carve a history of his own separate and apart from that of the Corps, still sporting a ring with an artificially induced weakness against anything made of wood. Honoring this separate history, the Guardians never moved to force Scott to relinquish the ring, formally join the Corps, or adopt its colors, although during the Rann-Thanagar War, it was revealed that Scott is an honorary member of the Corps.
Hal Jordan: The next Green Lantern to see publication was Harold "Hal" Jordan, a second-generation test pilot, having followed in the footsteps of his father, Martin Jordan. He was given the power ring and battery (lantern) by a dying alien named Abin Sur, whose spaceship crashed on Earth. Abin Sur used his ring to seek out an individual who was "utterly honest and born without fear" to take his place as Green Lantern. Jordan became a founding member of the Justice League of America and as of the mid-2000s is, along with John Stewart, one of the two active-duty Lanterns in Earth's sector of space.
Jordan was also a member of the Green Lantern Corps, which was modeled after the "Lensmen" from the science fiction novel series written by E.E. Smith. The early 1980s miniseries "Green Lantern Corps" honors this with two characters in the corps: Eddore of Tront and Arisia. A different interpretation of Jordan and the Corps appears in Superman: Red Son.
Following the rebirth of Superman and the destruction of Green Lantern's hometown of Coast City in the early 1990s, Hal Jordan seemingly went insane and destroyed the Green Lantern Corps and the Central Power Battery. Now calling himself Parallax, Hal Jordan would devastate the DC Universe off and on for the next several years. However, after Earth's sun was threatened by a Sun-Eater, Jordan sacrificed his life, expending the last of his vast power to reignite the dying star. Jordan subsequently returned from beyond the grave as the Spectre, the divine Spirit of God's Vengeance, whom Jordan attempted to transform into a Spirit of Redemption, which ended in failure.
In Green Lantern: Rebirth, it is revealed that Jordan was under the influence of a creature known as Parallax when he turned renegade. Parallax was a creature of pure fear that had been imprisoned in the Central Power Battery by the Guardians of the Universe in the distant past. Imprisonment had rendered the creature dormant and it was eventually forgotten, becoming known merely as the "yellow impurity" in the power rings. Sinestro was able to wake Parallax and encourage it to seek out Hal Jordan as a host. Although Parallax had been trying to corrupt Jordan (via his ring) for some time, it was not until after the destruction of Coast City that it was able to succeed. It took advantage of Jordan's weakened emotional state to lure him to Oa and cause him to attack anyone who stood in his way. When Jordan finally entered the Central Power Battery and absorbed all the power, he unwittingly freed the Parallax entity and allowed it to graft onto his soul.
Guy Gardner: In the late 1960s, Guy Gardner appeared as the second choice to replace Abin Sur as Green Lantern of sector 2814. Gardner was originally supposed to receive Abin Sur's ring, but Jordan was closer. This placed him as the "backup" Green Lantern for Jordan. But early in his career as a Green Lantern, tragedy struck Gardner as a power battery blew up in his face, putting him in a coma for years. During the Crisis on Infinite Earths, the Guardians split into factions, one of which appointed a newly revived Gardner as their champion. As a result of his years in a coma, Guy was very emotionally unstable, although he still mostly managed to fight valiantly. He has gone through many changes, including wielding Sinestro's yellow Qwardian Power Ring, then gaining and losing Vuldarian powers, and readmission to the Corps during Green Lantern: Rebirth. He later became part of the Green Lantern Honor Guard, and oversees new Green Lanterns' training. Gardner is designated as Green Lantern 2814.3.
John Stewart: In the early 1970s, John Stewart, an unemployed architect, was selected by the Guardians to replace a comatose Guy Gardner as the backup Green Lantern for Jordan. When Jordan resigned from the Corps for an extended period of time, Stewart served as the regular Lantern for that period. Since then, Stewart was in and out of action due to various circumstances, even becoming the first mortal Guardian of the Universe. He also joined and lead the Darkstars when the Green Lantern Corps were destroyed by Parallax. After that, he took over being Green Lantern for Kyle Rayner when he left Earth, also taking his place in the JLA. Now he has begun serving with Jordan as one of his sector's two designated regular-duty Lanterns designated as Green Lantern 2814.2.
Kyle Rayner: A struggling freelance artist when he is approached by the last Guardian of the Universe, Ganthet, to become a new Green Lantern with the last power ring. Ganthet's reasons for choosing Rayner remained a secret for quite some time. Despite not being cut from the same cloth of bravery and fearlessness as Hal Jordan — or perhaps because of that — Rayner proved to be popular with readers and his fellow characters. Having continually proven himself on his own and with the JLA, he became known amongst the Oans as The Torch Bearer. He was responsible for the rebirth of the Guardians and the re-ignition of the Central Power Battery, essentially restoring all that Jordan had destroyed as Parallax. Rayner later began operating as the Green Lantern known as Ion.
Kyle Rayner was chosen to wield the last ring because he knew fear, and Parallax had been released from the Central Power Battery. Ganthet knew this and chose Kyle because his experiences dealing with fear enabled him to resist Parallax. Because Parallax is a manifestation of fear, and yellow, none of the other Green Lanterns, including Hal, could harm Parallax and, therefore, came under his control. Kyle taught them to feel and overcome fear so they could defeat Parallax and incarcerate him in the Central Power Battery once again.
Kyle became Ion, who is later revealed to be the manifestation of willpower in the same way Parallax is fear. During the Sinestro Corps War between the Green Lantern Corps and the Sinestro Corps, Ion was imprisoned while Parallax possesses Kyle. In Green Lantern (vol. 4) #24, Parallax consumes Hal Jordan. Hal Jordan enters into Kyle's prison, and with his help, Kyle finally escapes Parallax.
Afterward, Ganthet and Sayd trap Parallax in the Lanterns of the four Green Lanterns of Earth. Ganthet asks Kyle to give up his right to be Ion and become a Green Lantern again. Kyle accepts, and Ganthet gives Kyle a power ring. Kyle is outfitted with a new costume including a mask that looks like the one from his first uniform. Kyle is now a member of the Green Lantern Corps Honor Guard, and has been partnered with Guy Gardner.
Kyle now shows up mostly as part of the ensemble cast of Green Lantern Corps. Corps rookie Sodam Yat took over the mantle of Ion. Sodam has made an appearance in the Legion of Super Heroes Final Crisis tie-in Legion of Three Worlds as the last surviving Green Lantern/Guardian of the Universe.
Kyle is designated as Green Lantern 2814.4 within the Corps.