Itachi is an ex ninja from the Village Hidden in the Leafs (Konoha). I'm saying ex because one day when he still was in Konoha, Itachi killed he's entire clan except his little brother Sasuke. Maybe the reason Itachi didn't kill he's brother is that when Sasuke grows it can kill him. After Itachi made this massive murder he escaped from Konoha and short after that he joined the organization "Akatsuki". Uchiha Itachi is a strong ninja witch uses Genjutso and has the unique tehnique "Mangekyu Sharingan" with it he can torture the enemy's mind.