The Kelvin Timeline' (aka Kelvinverse, JJverse or alternate reality) is the name of the alternate universe created by the incursion of the Romulan Nero. It first diverged from the prime universe in the year 2233.
The diverged universe began when the Romulan mining vessel the Narada attacked the USS Kelvin. Because of this, James T. Kirk never knew his father and grew up with his abusive uncle, which changed the history of this famous captain of the Federation.
Shortly after 2258 and the destruction of the planet Vulcan, the Second Earth-Romulan War was declared. This one resulted in the complete decimation of the naval forces of the Romulan Star Empire. At the forefront of the invasion was the USS Enterprise, captained by James T. Kirk.
By 2285, James T. Kirk had become a hero of the Federation for his actions during the Second Earth-Romulan War, as well as many numerous explorations and discoveries. Most of the rest of his career was much like that of his prime universe counterpart, except that he died in combat with K'Grall during the Federation-Klingon war that erupted after the destruction of the USS Enterprise.
With the launch of the USS Enterprise-B, the Federation's position in the war fell drastically. Captain Harriman's first command lasted only three hours, during which he openly declared allegiance and support to the Order of the Master Race and turned the ship against Earth to secure his place as president. But Demora Sulu gave her life to save the world from what Harriman might do and destroyed the Enterprise. Because of the loss of one of their finest ships, the Federation fell under even heavier attacks from the Klingon Empire.
In 2344, after a long career that began in 2320 with the captaincy of Montgomery Scott and ended with Rachel Garrett, the USS Enterprise-C was destroyed by a band of Romulans during the Battle of Narendra III. Certain members of the crew were taken captive by the Romulans, and were later incarcerated in their hold. One of them, Edward Shield, managed to escape and returned to Federation space. But when he discovered that the Federation never even tried to rescue them, he became dissatisfied with what he believed to be a corrupt Federation and became an outlaw.