who organizes it?
The FAI Gliding Commission.
World Gliding Championships
The World Gliding Championships (WGC) is a gliding competition held every two years or so by the FAI Gliding Commission. 
how long do gliders stay in the air Glider pilots can stay airborne for hours by flying through air that is ascending as fast or faster than the glider itself is descending, thus gaining potential energy. is it a sport? Yes, a competitive air sport. how is it done? Pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. does it face any challenges? UNANSWERABLE are there any competitions of it held? Local and national competitions along with biennial World Championships. what is the championship mentioned about? It is a gliding competition held every two years or so.
wiki:21129972
World Gliding Championships [SEP] Introduction
The World Gliding Championships (WGC) is a gliding competition held every two years or so by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are sometimes held in the summer in the Southern Hemisphere.