While judo is indeed a martial art, it closely resembles wrestling, in that there is very little striking involved - only grappling.
Judo became an Olympic sport in 1964.
A judo player (judoka) can aquire grades, each rewarded by a special colour belt. There are two divisions of grades, the student grades (kyu), and the master grades (dan). The first six dan grades wear the Black Belt, and the higher grades wear larger double width belts.