When Barry Allen was only eleven, his mother was killed and his father was arrested since the police mistook him for the murderer. Barry refused to believe his father was guilty and became a forensic scientist since he dedicated himself to finding the real murderer as well as helping other people in his situation.
Barry would have a well known habit for slowness and lateness which would annoy his girlfriend Iris West. Working late one night, a rack of chemicals Barry was working on became struck by lightning which led to him having the ability to move at a super speed. Barry became a vigilante known as the Flash, the fastest man alive. Drawing energy from the speed force, Barry started to protect people from Central City and became one of the people who started the Justice League. Barry is a key part in the universe because after changing the time stream for the worst he saved it and changed things back to the way they were.
Barry was a fan of comic books and the hero of Jack Garrick the Flash. Barry experimented with his powers to find he could vibrate his molecules enabling him to appear invisible and phase through solid objects. Barry could also quickly think and process information at light speed. Iris' foster father scientist Ira West created a suit to deal with his powers and chemically shrunk it so it could fit in a ring so Barry can easily carry it. Barry even constructed the Cosmic Treadmill to travel to other dimensions.
After the events of Flashpoint where Barry altered the time line to save his mother, Barry created a new one in which the entire universe has been compressed and altered into a five year timeline. A few changes started to occur: Barry is adopted by Darryl Fyre after his father was wrongly accused of murdering his mother and used his adopted father's connections to become a forensic scientist. During Barry's college years, he met Manuel Lago at a party and became close friends with him. Barry lost touch with Manuel when he entered a military program. For years Barry would visit his father in prison, much to his fathers pleads to terminate his investigation and move on, Barry would work in his science lab during his spare time to capture the real person who killed his mother. One night, Barry got angry and threw one of his machines out the window causing a lightning bolt to shoot into the lab, hit him, and dose him in chemicals granting suicide. Barry became the Flash and later joined the Justice League to stop Darkseid attacking Earth and was the League's founding member.
Also in the New 52 Universe, Barry Allen from the future went back in time to kill his foes after Wally West died and due to guilt for not saving him.
The Flash (2014)
In an attempt to murder Barry before he becomes the Flash, Eobard Thawne traveled back to the year 2000 to murder Barry as a child. Future Flash followed him and attacked him inside the Allen House. When the 11 year old Barry comes into the room to check on his mother, Nora ends up being in the center of the room surrounded by red and yellow streaks of lightning. Eobard tries to kill the young Barry until Future Flash took his younger self 20 blocks away to safety. In anger for failing to kill Barry, Eobard killed Nora instead. In Fast Enough, Future Flash realized another version of his younger self was trying to change the time line and forbid him from doing it since he knew that would cause more harm than good.
-Harrison Wells in the Flash was thought to be an older version of Barry Allen from the future.