Canyoning involves the use of abseiling, jumping and sliding to get from the top of a canyon to the bottom.
It involves the use of mountaineering and white water skills to successfully descend a canyon, and canyons can be anything from a steep wide open river, to a deep narrow slot canyon only a couple of feet wide.
Gorge walking could be considered an element of canyoning, and usually involves ascending an easy angled stream without the use of any ropes or other technical equipment.
Most importantly canyoning is a lot of fun.