What is the difference between
Sport Climbing and
Traditional (Trad) Climbing? Is it just that
sport climbing uses bolts?
Both, sport climbing and trad climbing are a form of lead climbing, which means the first climber to go up is not protected by a rope from above. A sport climber just uses carries quick draws that, as you mentioned, get clipped to bolts that have been placed in 10 to 15 foot intervals. At the end of the climb, a sport climber can expect to find a belay anchor consisting of two to three bolts with rappel rings that he/she uses to build an anchor.
A trad climber carries not just quick draws, but a whole rack of climbing gear consisting of cams, nuts and hexes that get placed into cracks in the wall. In difficult to protect places there might be a bolt that has been placed by the first ascent team. At the end of the climb or pitch (one rope length on a multi-rope length climb) a trad climber often has to build an anchor with the trad-gear, but sometimes, just like in sport climbing, routes have belay stations with two to three bolts.
Sometimes the classification of sport and trad climbs gets a little messy. In Joshua tree for example, guide books refer to some climbs as "bolted climbs." These climbs are by no means sport climbs, even though the only means of protection on these routs are bolts in the rock. The difference is that those bolts are spaced 30 to 60 feet apart, which means the leader might fall up to 120 feet.
Often sport climbs were rap-bolted, which means the first ascent party rappelled down the rout, placing bolts on their way down. Traditional climbs get established from the bottom up, which means the first ascent party placed bolts they deemed necessary as they were climbing up.