Ninjutsu

Ninjutsu (忍術, Ninjutsu? "Ninja Techniques") vaguely refers to pretty much any technique that uses chakra and allows the user to do something that they otherwise would be incapable of doing. Unlike genjutsu, which makes the opponent see illusions, the effects of ninjutsu are quite real. Ninjutsu relies on chakra and, most of the time, hand seals (each hand seal showing a different animal in the zodiac) to be effective. The hands are put in sequential positions that mold chakra in the necessary manner to perform a jutsu. This is not always consistent, however, and some of the simpler jutsu seem to become second nature to experienced ninja, after which they can perform them at will. Additionally, some ninjutsu can be classified as an elemental jutsu, in those cases where a specific element (wind, water, fire, earth, lightning) is used.

Technique
Jutsu, or skills/techniques, are the mystical arts a ninja will utilize in battle. To use a jutsu, the ninja will need to use his chakra. Chakra comes from two places. (1) the body energy inherent in your trillions of cells and (2) the mental & spiritual energy gained from exercise and experience. To perform a jutsu, the ninja will bring out and releasing these two energies. By forming handseals, the ninja is able manifest the desired jutsu. Because of the extensive number of hand seals and different combinations, there are thousands of potential jutsu to be discovered.

Ranks
E Rank: E Rank Jutsu are learn by Academy Student which are the basic and most fundamental Jutsu for all graduating ninja. EX: Clone Jutsu & Transformation Jutsu

D Rank: D Rank Jutsu Genin level technique and can be achieved by all Genin, though a many ninja only learn their "type" of technique. EX: Earth Style: Head Hunter Jutsu

C Rank: C Rank Jutsu are base on Chunin level technique though some Gennin can perform this and some Chunin cannot. EX: Fire Style: Fireball Jutsu

B Rank: B Rank Jutsu are Jonin level technique but Naruto can also perform this technique, which show his intelligent. EX: Shadow Clone Jutsu

A Rank: A Rank Jutsu are Elite Jonin level and up, even including some Forbidden Technique. Some Elite Jonin and Missing Ninja will create their own technique as their "Trump Card" or even forbidden one.

S Rank: S Rank are Secret, forbidden high class level technique. This rank technique is mostly known to only 1 or 2 ninja.