A brilliant scientist on the planet Krypton, he learned that the planet faced destruction and had attempted to warn the Science Council which governed the planet. The Council dismissed Jor-El's findings as faulty and even dared to accuse him of treason. Only as the Kryptonian apocalypse was upon them did they realise the truth, and by then it was far too late to evacuate the planet's population.
However, Jor-El still believed that it was possible for Krypton to survive through his new-born son Kal-El. He had constructed a small capsule that would send his child to a faraway planet - Earth - where he would grow up learning human values. Not only that, but Kryptonians gained extraordinary abilities when in the presence of a yellow star, so Kal-El would be blessed with incredible powers. It was Jor-El's wish that his son grow to learn wisdom and compassion and use his powers for the benefit of the people of Earth, a wish that Kal-El would strive to fulfil throughout his life.
Jor-El only built a single small capsule for his son which also contained Kryptonian garments that he would wear to symbolize hope for humanity as well as crystal-tech containing information about Kal-El's place of birth. As Krypton imploded, Jor-El launched his son's capsule into space and stood side-by-side with his wife Lara as their world died around them. Although Jor-El died along with the rest of Krypton, he was still able to offer his son help in the form of an artificial intelligence embedded in a computer storage device that he placed inside his son's space capsule. This AI possessed all of Jor-El's memories and mannerisms, allowing Superman to learn about his people and their past as well as warning him of several extra-terrestrial threats he would contend with in the future.
In most versions of Superman, Jor-El dies as Krypton is destroyed, whether it be by explosion, implosion, burial, etc. However, in Man of Steel, Jor-El (played by Russell Crowe in this version) dies before the planet's destruction when he is murdered by General Zod, who impales him with a blade.