It is a combination of resistance and balance because your body is suspended in the air as you glide on a string.
You basically have to move back and forth between three strings. Tibetan bridges manage two strings which are parallel on the same level where you will place your hands, like a handrail. The third string is right between the other two and allows your feet to rest as you cross the bridge.
The feeling is very similar to what tightrope walker may experience but without danger of falling because there is an additional safety rope in case of loss of balance. Practising this sport allows you to cross vertical steps, ravines, inaccessible cliff with any other means.