Rebelling against something means believing or acting in a way that is opposed to the majority. Rebelling against prevalent systems requires one to have the courage enough to break conventions through actions as well as beliefs.
Every social order has its share of rebels. This kind of agitation usually contributes to the evolution of a society. If it weren't for people who opposed conventions, things would always remain the same! There wouldn't be growth or change, and that would result in stagnation. However, being rebellious does not have to mean being an outcast. You don't have to live on the streets while on holiday in Holland. It is possible to find good old traditional Amsterdam Hotels , and rebel constructively against the system.
Rebellion is in the mind. Of course, it needs to be translated into action as well. But to be able to rebel, one must fully understand the convention. It is important to understand how society works, and even more important - understand the thing that you're rebelling against!
Without understanding this, one is simply doing someone else's bidding, indeed like a headless chicken! And obviously, rebelling just because someone tells you to, is not really rebelling at all. In fact, it is following convention!