Martial arts are practices from different traditions for actual Combat. All Martial arts share 1 common objective which is to defend and defeat your opponent. Martial arts can also be a deadly weapon if the Martial Artist don't have a pure mind.
In modern days, martial arts are more commonly practiced for Health reasons, Combat Sports and Training of the Mind. Most importantly in choosing which school to join is depending on one's interest, some of us might have injuries with our legs or arms and some with a weak body. I would suggest that before engaging in any school is to browse through the web or you tube and check on more details on the Martial Art itself.
Martial Arts are divided into 2 Category - Armed (Archery, Bo, Nunchakus, Fencing etc..) or Unarmed (Dance, Tai Chi, Combat Sport, Kickboxing etc..) Some of us might wonder if there is any Martial Arts in a form of Dance, you can check for more details for Capoeira (developed in Brazil) or Dirk Dance from Scotland
Some parents would feel that it would be dangerous for their kids to learn martial arts as it serve for another reason for the kids to start a fight at school. But frankly speaking, it depends on the individual understanding in Code of Honour. Martial Arts is not about picking a fight, but to defend yourself and your love ones in critical conditions. Plus there is no real danger in Martial Arts itself if one has proper protection pads and so on...
The methods of training in different school will include simulated combat or routines of techniques known as Kata. This page is where on all of these.. Stay Tuned!