Via ferrata, or Klettersteigen in the German speaking parts of the alps, is a sport somewhat in between walking and climbing. It is easiest described as a simple climbing route, usually filled with lots of metal supports for you to hold and stand on. This is what the name via ferrata (translated: iron road) comes from. They are usually graded a 1 to 5 (or A to E), where a 1 is usually easier then some complex walking routes, and a 5 is similar to a grade 3 (or maybe 4a) climbing route.
Unlike climbing, where you will need full equipment (including ropes) to belay, a via ferrata is belayed by clipping two carabiners into a cable stretching all along the route. This cable is attached to the wall in strategic places. In a fall, your carabiners will fall onto such an attachment and brake your fall from there. When passing such a point, it is important to move your carabiners one by one, so one always stays attached.
The easier klettersteigs are very suited for climbers without much experience, because of the easy climbing and the little requirement for skill and knowledge regarding safety. This way, beginner climbers can also reach places that are usually only reachable by experienced climbers and alpinists. Other, more fun-oriented klettersteigs, are filled with rope bridges, ladders and other fun elements you wouldn't normally conquer without your safety devices.
These falls can get pretty big, as these attachments can be spaced out pretty far. To make sure your fall can be safely broken and held, you use a special via ferrata set, or klettersteigset. This set contains a stretch of tape, folded in half, and sewed together. When you fall, this tape will tear apart, breaking your fall. This mechanism can only be used once however, so after a fall you will either need to request a rescue (possibly via a helicopter), or belay the rest of the route via other means. A complete list of klettersteig equipment contains:
For simple klettersteigs:
There is no course needed to go and klettersteig. However, for more advanced klettersteig routes, it is advised to bring a subset of full climbing equipment, at least enough to perform a simple rescue and belay your partner until the end of the route. This is only applicable if a rescue by a third party is very difficult or takes very long, and you have sufficient knowledge of how to handle such a rescue and handle yourself in alpine conditions after the rescue. Of course, it is advised to only go and step into such a route when your material, knowledge and skills are sufficient. The courses in the climbing track can prepare you with these skills and knowledge, though the materials you need to buy yourself.