Judo is a Japanese martial art and combat sport created by Jigoro Kano in 1882. He compiled techniques from different jujitsu styles and adapted them for safer training. Some key principles of judo include yielding to an opponent's strength to use their energy against them, and non-resistance to safely practice techniques without injury. The document also discusses how judo has been the author's hobby and passion since childhood, and they hope to compete internationally as a woman to inspire others.