My kid used to take Karate, but I never learned much about it.
Ok, let me tell you about it's origin, Karate was brought to Japan in the early 20th century 
I know there are different colored belts depending on skill, but I only remember his last one was brown.
Ryukyuans from Okinawa that went to look  for work in Japan took it there
How is it different from other things like Jujitsu, Kung Fu, etc? 
It was  taught in Japan after the Taishō era.
So it's been around for a long time, then.
yes, in 1922 the Japanese Ministry of Education invite someone to give a demonstration about it