Ninjutsu is really a type of technique in where you use hand signs and focus your chakra to create the desired technique.
I changed it a little to apply to Battlefront 2.
Ninjutsu is the art of Medium range fighting. You will learn things that will help you in medium range fighting.
How to keep your enemy at medium range.
How to stay calm and aim your shots.
There is much more. Ask your Jounin instructor for more information.