The Mangekyo Sharingan is an advanced form of the sharingan. To obtain the mangekyo sharingan you must feel the emotoin of losing a friend or family. Uchiha throught history killed their friend of their family member just to obtain the mangekyo sharingan. Itachi Uchiha obtained his mangekyo sharingan by killing is best friend Shisui. After obtaining the mangekyo sharingan Itachi was able to use three powerful techniques. With his left mangekyo sharingan he is able to use Tsukuyomi. With his right he is able to uses Amaterasu. The last one is Susanoo.