In the first film, Jafar tries to use Genie's powers to take over Agrabah, first wishing to become the sultan, and then the most powerful sorcerer in the world. After battling Aladdin with his questionable sense of humor, Jafar transforms himself into a giant cobra in an attempt to kill Aladdin, but just as Jafar is squeezing him to death, Aladdin tricks Jafar into using his third and final wish to become an all-powerful genie himself and the strongest entity in the Disney universe. In Western culture, genies are almost always portrayed as being confined to small oil lamps until they are released to do a human's bidding; Jafar is therefore trapped by his own selfish wish for power.
Jafar is more a present part of the plot than other Disney villains, especially during the era in which he was created, with proportionately more airtime than most other Disney villains. Many scenes featuring Aladdin are mirrored with scenes featuring Jafar, back to back, in which one can see Jafar's interactions with other characters, giving the viewer a more "personal" experience with the villain. His unique characteristics compared to most Disney villains are probably the reason that he lived at the end of his movie, at the same time arguing with Iago ("Get your blasted beak out of my face!" "Oh, shut up, you moron!" "Don't tell ME to shut up!").
In The Return of Jafar, the now-genie Jafar is released by Abis Mal, and, after cunningly making Abis-Mal waste his first two wishes, threatens Abis into helping him. His plan included kidnapping (and in some instances, replacing) the royal family and framing Aladdin for the Sultan's "death," which would have caused him to be beheaded, but (with help from a reformed Iago) the heroes manage to escape. When Jafar discovers this, he opens up a fissure into the earth in order to destroy Aladdin and the others. Believing to have won, Jafar is surprised to see Iago genuinely helping the heroes and shoots down his former ally with a fireball as Iago grabs the lamp. A mostly-dead Iago manages to kick the lamp into one of the lava pits, melting the lamp into nothingness. With a scream of anger and fear, Jafar disintegrates in a burst of light and disappears.
Jafar later made one more attempt at revenge in an episode ("Hercules and the Arabian Night") of Disney's Hercules TV-show spinoff, where he is temporarily revived by Hercules's arch-enemy, Hades, although he lost his status as an all-powerful immortal genie when he died. The two villains team up to get rid of Aladdin and Hercules by having them fight against each other, but their plan fails and Jafar ends up dead again when Hercules snaps his staff in half, and has not at this point made any reappearances in the official Aladdin continuity.
As far as Jafar's family goes, he has a fraternal twin sister named Nasira who tried bringing her brother back to life in the game Nasira's Revenge. Jafar's sister is very similar both in appearance and actions as Maleficent. She respects Jafar and the sibling bond between them is very strong.
Despite his magical aspirations, Jafar is actually incapable of performing any supernatural feats during the majority of Aladdin. He is shown to be scholarly and learned in arcane lore, his secret chamber filled with strange devices and stacks of tomes, and, as such, he operates more on the level of an alchemist throughout the film’s duration than an actual magician. Instead of casting spells, he relies on previously prepared potions capable of producing magical phenomenon, dropping a vial of red liquid on the floor, for example, in order to create a cloud of smoke. He also relies heavily on certain relics in his possession, such as his snake-headed staff which is capable, through its enchanted ruby eyes, of hypnotizing people. A gigantic hourglass which he keeps in his study also serves as a crystal ball for him, granting him the ability to see the outside world. He is also a master of disguise, assuming the appearance of an old beggar man in order to gain Aladdin’s confidence. He operates largely through his underworld connections, such as with the thief, Gazeem, as well as his position of authority within the palace, which places the entire Royal Guard under his command.
This inability to perform real magic is primarily what drives Jafar to search for the Genie’s magical lamp, and after achieving it, his second wish is to become the world’s most powerful sorcerer. After he makes this wish, he is noticeably able to perform a radical assortment of spells on a mere whim, such as physically manipulating physical bodies, levitating objects, spitting fire, materializing weaponry from thin air and, most impressively, shapeshifting into an enormous serpent. During this stage, he is never again forced to rely on his talismans, potions, or disguises.
In The Return of Jafar he is depicted as being a genie of almost unlimited power, easily defeating the Genie with a musical number ("You're Only Second Rate") and imprisoning him in a magical orb. Though he seems to be bound by the same rules as the Genie (most notably being unable to kill) Jafar easily finds ways around these limitations, such as transporting the bandit Abis Mal underwater when he wishes for sunken treasure and threating to let him drown.
His most recent appearance, Hercules and the Arabian Night, he has lost his status as a genie. However, he is still able to perform magic with his staff, although it is not as good as when he was the world's most powerful sorcerer. Here he is able to summon giant monsters, fire nonfatal blasts of red energy, and freeze things in blocks of ice. It seems likely that this magic was provided by Hades when he revived Jafar.