What is the Redbelt?

In Judo a Red Belt signifies the 9th and 10th dan ranks, i.e. 9th and 10th degree black belts. They are only optional however, and I think it's common to wear the black belt for training and the red belt only for ceremonial purposes. I'm pretty sure it's the same in Jiu Jitsu.

In other words it just signifies the top 2 ranks in the martial art.

It is entirely dependant on the style of the martial art in question. There is no universal "Official Jiu Jitsu" style, rather you have many ryu within a style, or schools as they ae translated as. The soke, or founder of the style can decide him/herself what the grades are, and what belt to award. Obvious tradition of white/yellow upwards to black is commonly held throughout, however the use of the fabled redbelt is entirely at the schools discretion.

Judo may have 10th dan etc is some schools but in my school of Jiu Jitsu 'Seishin Mizu Ryu Tatakai Jutsu' (a splinter of The Jitsu Foundation) there are only 5 dan grades and no redbelt.

We use the redbelt however in competitions, in fights we (in my style, again it could be different depending on the soke) use white and red belts to denote the fighters, regardless of their grade before.

In this film I believe redbelt is meant to denote some wh has been a teacher at black belt for 48 years. However I picked that up on IMBD so I don't know the truth of that statement.

Hope this helps

Matt

They got the idea from the red belt in Brazilian Jiu Jitsu. I know a few other systems have it, but with the influence of BJJ on MMA, I am sure they were thinking of the BJJ red belt. There have only been a small number of red belts in the entire history of BJJ. I believe just 2 or 3 (and I am referring to the 10th degree all-red belt, not the red/black belts under that). Helio Gracie (Royce's, Rickson's, Rorion's, and Royler's father, Renzo's uncle, etc...) just passed away less than 2 months ago. He was one.

I've done plenty of BJJ as part of overall MMA training, but that was all no-gi, and entirely focused on how it relates to MMA. Wasn't much up to speed on belt rankings within the system. Don't really care for belt rankings, actually. In BJJ, they are an EXTREMELY more reliable indicator of skill than in most other martial arts systems you can find instruction for in the US. So I do not mean to disrespect the belt system in BJJ. In fact, it is the only one I actually do respect. I just wasn't into the whole belt-ranking thing. Been there, done that, over 15 years ago as a karate black belt and instructor. Got pretty damned sick of the whole belt ranks thing.