Jujitsu or Jiu Jitsu is an umbrella term for a group of Japanese martial art styles, which if translated, means the 'art of softness' or 'a way of yielding'.
The primary idea is to fight with either an armed or an unarmed opponent, sans weapons, inspired from the techniques used by the Samurai in feudal Japan. It therefore involves pins, joint locks, and throws, and using the attacker's energy against him. Now, this art is practiced in its traditional as well as modern form.
Subsequently, there are belts symbolizing the level of learning, as in other martial arts. The belt colors are the indicators of the level of a jiu jitsu practitioner. It starts from white and goes on to black.
The things taught under the purview of white are a couple of strikes, punches, kicks and blocks, along with some basic throws.
A couple of hip throw variations, with some innovations to try out, are a special part of this belt. Once this level is passed, one normally gets enough in his arsenal to apply to any situation.
At this junction, an individual has to be prepared for any attack, and apply any throw as he deems necessary.
This is a fairly advanced stage, and many things from jumping double roundhouse to head, hip, and knee throws, to triangle choke are taught. From green onwards, the time between the exams increases considerably. At least 6 months to 1 year practice is required at each stage from here on.
During this stage, sparring weapon usage and extremely technical and complicated throws are taught. Ground fighting too is an important part of the training at this stage.
These were the traditional jujitsu belts. Brazilian jujitsu belts start from white and then directly progress to the blue belt, the rest of the order being the same. The reason is, Brazilian jujitsu is a descendant of traditional jujitsu.
Eventually, as you move higher up on the scale, one is expected to be better at the trade, and that only comes with perseverance and practice.