Thats Tony Bou, four (five?)times World Champion for Montesa and 4 times World Indoor Champion. It has been called Observed Trials since around the period after World War I before that it was called Reliability Trials starting around 1900. It is an amazing sport. Having done it (poorly) since 1974 and worked with National Champions, and near Champions as well as helping at US events with several World Champions all I can say is if you have not seen a top level Trials event, national or World you are missing an adventure in motorcycling. They literally defy gravity, the seeming availability of traction and can ride places with absolutely no continuous path of travel. They can go up a cliff skiping from point to point, turn in mid air in less than the length of a motorcycle, and drop off shear cliffs.
The sport is an amazing triaing ground for other riding. You perfect clutch and front brake skills, weight shift for traction control and learn delicate throttle control. Skills you cna use over and over no matter what you ride. You don't need the latest bike and you don't need a big area. Riding figure eights in a drivway will teach you loads. Find somone with a trials bike and have them take you out for a ride!