As gaara saw legendery yellow flash and listened to him, Without any emotions he started to talk
So where should i begin ?! guess i will tell everything i know ! Genjutsu, literally meaning Illusionary Techniques is, the art of creating illusions in the victims mind by inserting the users chakra into their brain and creating images that aren't real, illusions, depending on the grade of the genjutsu, the user can manipulate all the 5 senses of the victim, making them feel pain, blindness, etc, genjutsu can be dispelled by stopping the victim chakra flow for a moment, to then reatain it normally, while the chakra that was used for the genjutsu is expelled, also with pain, this however, cannot work in Mangekyou Sharingan genjutsu, due to it's abilties, now, about genjutsu, there are other ways of them breaking the genjutsu and they can cast their genjutsus better than non-Uchihas by simply using eye contanct, which is why the Uchiha is the strongest clan in the Naruto Verse, talking again about Uchihas, there are 2 forbidden genjutsus which abide from the ordinary rules of use, being Izanagi and Izanami, Izanagi can manipullate reality, making it an illusion and changing it into another one which the user so wants, Izanami makes an almost endless cycle in the victims mind, till they see recognize their flaws and then they can get free, both of them at the cost of the vision of the eye used in it.