All martial arts were originally developed for combat or to provide some type of self defense. Many arts have changed and evolved over the years, developing competitions, and tailoring the practice of the art to perform in competitions rather than combat.
When you are looking for a martial art to study, you need to understand what you want to get out of it. Fitness, self-defense, do you want to compete, etc… and then find a school that has the same focus as you. Most martial arts will provide all of these for you, but the focus may change depending on the art, and the school decide on.