For fans who need a quick recap, John raised his sons to fight the supernatural— Sam and Dean’s mom was killed by a demon named Azazel — but he disappears in the first season, prompting Sam and Dean to head out to in search of their dad. They eventually find each other and join forces to locate the Colt, a gun capable of killing anything, including Azazel.
Fast forward, John is captured and possessed by the demon when Sam and Dean come to his rescue. However, Sam is unable to shoot his father (and Azazel in turn) with the Colt, so the demon escapes and the trio are involved in a car crash as they attempt to escape.
This leads to Season 2, when John makes a deal with Azazel to save Dean, who is comatose following the accident. John agrees to give up his life, soul, and the Colt to save his son’s life. It’s not until the end of the second season that John is able to escape Hell and save a now-possessed Dean, who is finally able kill Azazel with the mythical gun.
The last fans saw of John, he was smiling at his boys before being engulfed by a white light.