The so called Bullet train in Japan?

Hello! I've just seen an announcement for a documentary on Japanese Bullet trains. It's tomorrow but I won't be able to see it so can you tell me what are these bullet trains and why are they called that way? If you could provide me with any info it would be really nice! Thanks in advance!

Hi! The explanation is very simple, theyre fast as bullets. Nowadays they reach speeds over the 300km/h. Nozomi is the fastest, because it stops only at the biggest stations, Hikari needs about 3 hours to reach Osaka if youre going from Tokyo, and Kodama is the slowest of them all. It stops on every side station.