Short answers, pulled from the story.
According to John Clements, the term martial arts derives from an older Latin phrase meaning the arts of Mars, in reference to the Roman god of war. It was used for the combat systems of Europe as early as the 1550s.
Unarmed martial arts fall into those focusing on strikes, those focusing on grappling, and hybrid arts covering both. Striking arts include Boxing, Muay Thai, Karate, and Taekwondo, while grappling arts include Judo, Sumo, Wrestling, Brazilian jiu-jitsu, and Aikido.
Kano Jigoro established the Kodokan School of judo in 1882, beginning the sport of judo. He had studied older forms of jujutsu before founding his school.
Bruce Lee is credited as one of the first instructors to openly teach Chinese martial arts to Westerners. His films drove the kung fu wave of Hong Kong action cinema in the 1970s, which popularized martial arts in global popular culture.
The 100-man kumite is the ultimate challenge in Kyokushin karate, in which a challenger completes 100 continuous rounds against fresh opponents, often with minimal or no protective gear. Only 30 people have successfully completed it.
Hundreds of millions of people worldwide practice some form of martial art. Web Japan claims 50 million karate practitioners worldwide, and the South Korean government estimated in 2009 that taekwondo is practiced by 70 million people in 190 countries.
In full-contact sparring, strikes are used with full force and the aim is to knock out or force submission of the opponent. In light-contact sparring, force is restricted to touch contact and a punch is pulled before contact, with winners decided on points.