Err, gliders can't go places - they have no engine...
Oh, but they can. The British distance record is over 1,000km and the world record, set in New Zealand, is over 2,000Km.
Of course, the distance you can cover depends on conditions, skill and a healthy slice of luck. Competition flying puts up to 100 pilots together to race around a set task, the fastest glider being the winner (except that there is usually an ingenious handicap system, so a K8 can compete with an LS8 - of course the LS8 always wins anyway!)
So, these tasks then?
Cross-country tasks consist of a start/finish line, usually the home airfield, and several turning points. Turning points are pre-defined ground features such as churches or other gliding sites. The glider has to fly around the far side and take a picture to prove that they have done so. The wonders of technology mean that you can just datalog satellite navigation to prove where you've been.
With the task marked on his chart, the intrepid glider pilot sets off. The pilot will climb until nearly at cloud base and then set off for the next good cloud at high(er) speed. This cloud will hopefully be right on track, but never is, so the pilot will fly along lines of thermal energy that are nearly on track and then 'jump the gap' to get back to where they are going. When the pilot rounds the last turning point they will take one final climb to allow them to glide back to the finish. Alterrnatively, the lift could die, the pilot having flown too fast between thermals or somehow something else will go wrong, ending up with a land-out and a pint in a local pub.