Aoba is a Special Jounin from the Hidden Leaf Village. He was an observer to the chuunin exam's final round. When the Hidden Sand and the Hidden Sound invaded Konoha he dispelled Yakushi Kabuto's genjutsu and helped fight against the invading shinobi. He's also the one that accidentally told Sasuke about Uchiha Itachi's visit to the Hidden Leaf, making Sasuke go search for his brother to get his revenge. But Sasuke not being strong enough is easily beaten, and Aoba was an idiot for mentioning it in Sasuke's precense.
In Shippuuden Aoba is a member of the Niju Shotai, a task force created by Tsunade to track down, capture or eliminate Akatsuki members in the Fire Country. He fights alongside Asuma Sarutobi and Raido Namiashi. He uses fire jutsus, and we also saw him use a technique similar to the Kage Bunshin no Jutsu. A technique where a large number of crows blocks the enemy's eye-sight. We saw him use this technique to disguise Raido Namiashi's movements. Just like with the shadow clones, the crows are dispelled when hit.