Genjutsu (幻術; ; Literally meaning "Illusory Techniques"; ) are techniques that are employed in the same fashion as ninjutsu, requiring chakra and hand seals. However, the primary difference between the two is that the effect of genjutsu is illusory, creating chakra imbalances in the victim's brain, causing a disruption in their senses. This is often used to create false images or cause pain from trauma (because the body is led to believe it is in pain), however there are plenty of other uses depending on the situation. They are not used as often as ninjutsu because they don't physically harm the opponent, but several characters have made themselves well known for their great prowess with genjutsu. Genjutsu is created when a ninja extends their chakra flow through the cerebral nervous system of their opponent to control their mind's chakra, thereby affecting their five senses.
To combat the effects of genjutsu, there are two options. The first option is for the ninja to stop the flow of chakra in their body, and then apply an even stronger power to disrupt the flow of the caster's chakra. This can also be done by an unaffected ninja. The second option is for the affected ninja to hurt himself or herself, and then utilize the resulting pain to bring their senses back in order (of the two options, the latter seems more effective in most situations, or at least is the easiest). Genjutsu attacks usually will require a lot of skill, and if performed incorrectly will not work; even Jiraiya had trouble performing such techniques. Genjutsu is most often used by ninja with very precise chakra control and very high intelligence.