Ninjutsu in a literal translation meaning ninja techniques; it relies on the shinobi's chakra system and handseal making for it to be effective as it should.
The hands are put in sequential positions that mold and manipulate chakra in the necessary manner to perform a technique. This is not always needed, however, and some techniques become second nature to experienced ninja, after which they can perform them at will.
Ninjutsu consists of two chakra transformations that are;
Shape transformation, which deals with controlling the form, movement, and potency of chakra.
Nature transformation, which usually deals with changing the physical properties of chakra into an element.
Techniques vary greatly in purpose, with the simpler ninjutsu serving such tasks as transforming the user or allowing them to evade attacks. These techniques are often second-nature for experienced shinobi, who can use them at will. More complex ninjutsu manipulate one's surroundings or utilise the elements, respectively serving such tasks as healing others or manipulating nature transformations.
One of the important subtechniques in Ninjutsu is Bukijutsu (weaponry), which allows the user to seal and summon a vast variety of ninja weaponry from scrolls. And one of the main reasons I want to master Ninjutsu; so I can create weaponry related customs for 1010
The most advanced form of Ninjutsu would be Rasengan, created by Minato and perfected by Jiraiya and Naruto.