Axton is originally from a planet named Hieronymous and spent ten years there with the Dahl military force. Due to his general disregard for others and pursuit of fame and glory, he was discharged from the military and also left by his wife. He decided to go AWOL and thanks to a broadcast by Handsome Jack, he learned of the Vault and decided to pursue after it.
Axton's action skill is called Sabre Turret, allowing him to place a turret down that shoots at any enemy within range. The initial duration it stays out is set at 20 seconds, with a cooldown of 42 seconds. With the Sentry skill, you can increase the duration to 30 seconds and with the Resourceful skill (and some other things), the cooldown can be reduced to 21 seconds. While the turret is kind of lackluster at the beginning, upgrading it with skills will allow it to be equipped with a Slag-firing gun, rocket pods and even a shield emitter.