Naruto would have been just another action anime without the help of Jutsu. These are techniques which the Ninja in the Naruto world learn. There are three types of basic Jutsus - Ninjutsu, Taijutsu and Genjutsu.
Ninjutsu usually uses chakra in order to create techniques. There are exceptions to this of course, which is using weapons like shurikens and kunais. Examples of Ninjutsu include Rasengan, Shadow Clone Jutsu, Chidori, and much more.
Taijutsu is normal physical combat that is used by Ninjas. It pushes the physical limit of a person in order to achieve incredible results. While Taijutsu does not always require chakra, it can be used in order to amplify the damage done by it. Examples of this are the Leaf Hurricane and Uzumaki Barrage.
Genjutsu messes with reality to confuse people. Unlike Ninjutsu and Taijutsu, where chakra isn’t always required, Genjutsu requires chakra. Anything that happens in Genjutsu is a mere illusion. However, being trapped in Genjutsu for long enough can break a person’s mind. An example is Izanami, which traps the opponent in an infinite loop of the same thing repeating over and over.
Despite there being only three types of Jutsu, the extent to which they can be modified is incredible and it can be seen how much fun Kishimoto had developing these techniques and their weaknesses. Jutsu can be a concentrated ball of chakra which rotates at an incredible speed or simply someone controlling bugs.
There is no limit to how Jutsu can be used as it even has variations, which each person can call their signature move, like Naruto adding the wind element to the Rasengan and Sasuke adding the fire element to the Chidori. The potential of Jutsu is unlimited, and this is what makes the show so much fun to watch.