Itachi was a true prodigy during his time at the academy, and quickly graduated and became a Chunnin. After ascending beyond Chunnin Itachi joined up with the ANBU squad and quickly rose through the ranks there. Itachi began to distance himself from his one time close brother, Sasuke, and one night in genocidal manner murdered the entire Uchiha clan, which set Sasuke against Itachi and on his quest for revenge.
It is later revealed that Itachi killed the clan because they were planning a coup on the leaf village and Itachi was working to prevent that. In the end Itachi dies by Sasuke's hands, just as he always wanted.
To be used in the Fourth Shinobi World War, Itachi (alongside others) is later brought back to the world of the living by Edo Tensai - a jutsu used by Kabuto to revive the dead and remotely control them. After triggering the Kotoamatsuki technique, Itachi breaks free of Kabuto's control and teams up with Naruto and Killer Bee who together defeat the revived Nagato. Itachi then goes on to have an abrupt and brief reunion with Sasuke, and together they are currently fighting Kabuto in his hideout.
Typically in games Itachi is portrayed as a villain and utilizes his signature style of fighting with genjutsu (illusion techniques) and going to his strongest genjutsu (depending on the opponent) called: Tsukuyomi, which is only available through the awakening of the Mangekyo Sharingan in members of the Uchiha Clan. This allows him to take his opponents to an alternate reality in which they endure three days of torture in 3 minutes time. Other then Tsukuyomi, he possess 2 techniques available to him through the Mangekyo Sharingan. A Ninjutsu called: Amaterasu, which can engulf anything he sets his sight on in black fire, which is said to be as hot the the Sun itself. A technique called: Susanoo, which activates on the condition of having used Tsukuyomi and Amaterasu previously and in any order, but while sustaing the same session of the Mangekyo Sharingan; Susanoo will create a gigantic ethereal warrior who will sorround Itachi's body and fight on his behalf with the Yata Shield (can reflect attacks) and the Totsuka Sword which anything it cuts is send into a blissful dream genjutsu forever inside the sake container from which the sword sprouts out from.
Doujutsu - This kind of Jutsu involves using ones eyes, and will recognize othersGenjutsu, Ninjutsu , andTaijutsu techniques to form a counter attack. Two examples of Doujutsu attacks would be Sharingan and White Eyes. Typically the only people who are able to use Doujutsu attacks are people born into a family that already knows it. Because these attacks don't require much chakra they can be used from long amounts of time, without tiring the user.