Many of the Martial styles today are hybrids of other fighting arts that have existed or do still exist. International travel in the ancient and the modern world allowed the transportation of ideas. This included knowledge of martial arts techniques. Knowledge of techniques originally developed in one country would be adopted (and in some cases improved upon) by neighboring countries. Over time these new systems branched out in their own way, becoming unique, martial arts in their own right.
Each martial art has something different to offer. While some styles are very traditional and steeped in history, others are much more contemporary.