Orochimaru is another one of the legendary ninjas of the leaf country. He was trained by the Third Hokage himself, until he left the village after being denied becomming the next Hokage. He then taught himself a lot of forbidden Jutsu's, one of which he uses make himself immortal so that he could take revenge on the Third Hokage.

Orochimaru allied the Hidden Village of Sound and the Hidden Village of Sand where Gaara, Kankuro, and Temari came from, and planned with the Kazekage to destroy Konoha. However, on the day of the match, Orochimaru, Kabuto, and Kimimaro killed the Kazekage and Orochimaru put on his clothes and pretended to be him at the chuunin match, betraying both the Sand Village and Konoha, and placing himself right beside the Hokage.

Like Jiraiya, Orochimaru can also do Summoning No Jutsu, but instead of summoning Toads, he summons Snakes. Orochimaru is always using the "Cursed Seal" on people. He used it on Sasuke, but only so that Sasuke would seek him out and work for him, or maybe so Orochimaru could steal his body and have the Sharingan for himself.

In his fight with the 3rd Hokage, he pulled off his face and revealed the face of a young woman. He also revealed the real reason he was after Sasuske... which is that he wants Sasuske's body. Kabuto is one of Orochimaru's followers. He is a spy but he doesn't want to expose his cover, that's why he purposely failed the Chuunin examination six times! But even though he is good at hiding, all the sensei know his secret.

Kabuto is actually a Genin, which is revealed in the manga, Volume 4, Issue 5, Page 59. The assumed Jounin level is because of a conversation Orochimaru has with Kabuto right before the final rounds of the Chuunin exam - it occurs in both the manga and the anime, and Orochimaru says "You may be stronger than Kakashi, but you are not at my level yet".

It would also be essential to mention that he's a very good medic, and Tsunade even says about him that he is far better than she was at the same age. Orochimaru uses his medical talents to perform a number of surgeries on himself (such as making his transfers to other bodies successful or taking care of him after the Third nearly killed him) and on a number of his most powerful followers (Kabuto maintained Kaguya Kimimaro's life when his mysterious illness took him).