Kung fu is a Chinese martial art, a style of fighting that involves special punches and kicks. You can learn kung fu for self-defense or exercise.
Kung fu comes from Cantonese, and it actually refers to any skill you learn through hard work and lots of practice. As a martial art, kung fu started in ancient China as defense against enemies, first only practiced by the elite, and later by ordinary Chinese citizens as well. Kung fu consists of hand strikes, blocks, and kicks, but if you learn this ancient technique, you'll also practice simple stances, breathing, and meditation.