Vie Ferrate are pre-defined pathes through a mountain wall or face with a pre-installed cable and artificial climbing aids. You wear a harness and a special biner set, so you’re anytime safely connected with that pre-installed cable.
Vie Ferrate like this one in Kandersteg are good for recreation days between “real” mountain climbs. For my taste, newer installations tend to provide too much metal and climbing aids like these bolts shown here. I prefer climbing on rock instead of metal. However, I enjoyed this Via Ferrata on that rainy day, and it made for a photo as well ;-).