What is the difference between Jiu-Jitsu and Brazilian Jiu-Jitsu?
Traditional Japanese Jiu-Jitsu is like a martial arts buffet - strikes, throws, weapons, everything. BJJ took one dish from that buffet (ground fighting) and perfected it obsessively. Japanese Jiu-Jitsu practitioners learn many things adequately; BJJ practitioners learn one thing deeply. The Brazilian version also tests everything through sparring, so you know what actually works under pressure.