The level, or the belt system: In Tae Kwon Do, everyone starts out as a white belt. They gradually try to come up and go up to the next belt to, at the end, towards the black belt.
One thing is that every school is a little different. Sometimes their belt system might be from white belt, to orange belt, to green belt, to purple belt, to brown belt. Some schools from white belt, to yellow belt, to blue belt, and maybe they might have a stripe; blue stripe, to red belt, to red stripe, and a pre-black belt, and then to the black belt.
Again, every school is a little different on the belt system, but usually it takes about, maybe two years or a little less than two years to become a black belt. Once you hit the black belt, it doesn't mean you're already a master of Tae Kwon Do.
Basically, when you get your black belt, it means that you've just finished your basic training. That means you know how to do a roundhouse kick, ax kick, back kick, and everything basic.
Once you hit the black belt, there are degrees of black belt. There is first degree, second degree, third degree, and up and up and up. The longer you train, the belt degrees go higher and higher.
One thing is, during the black belt, you learn more of an understanding of the techniques, such as how to use them, the right and proper timing and distance. Also, I believe, training longer helps you understand a little bit more of the philosophy of the martial art also so we become more mature and wiser for our life. I think that's what it is about reaching that black belt.