The three ground elements for a ninja is, Taijutsu, physical fighting with your fist and/or a weapon, Genjutsu, the ability to make your opponent see what is not there, to trick his brain, and to make him collapse in fear without touching him, and Ninjutsu, Chakra based attacks, which lets you use physical attacks, in a far more advanced way, than just hitting your opponent with your fists. Ninjutsu is builded up around the substance known as chakra, chakra is also used in Genjustsu, but in Ninjutsu it can be so many things, fire chakra, earth chakra, water chakra, lightning chakra, wind chakra or just chakra. Chakra can be used to change your appearance, or even make clones of yourself, it knows no limits.