Jafar is nothing, but pure manevolence and avarice. He's longed to be the ruler of Agrabah for a long time. His main counterpart Aladdin gets in the way of his plans so he tries to defeat him but fails. Jafar at the end is sent into a small lamp because he turned into a genie.
He returns in the sequel, The Return of Jafar. Once again, Jafar tries to rule Agrabah and get Aladdin killed. However, in the end, he is destroyed when Iago drops his lamp to the lava.