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 uses quickdraws which, 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 quickdraws, but a whole rack of climbing gear consisting of cams, nuts and sometimes 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 National Park in California 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 routes 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 are rap-bolted, which means the first ascent party rappelled down the route, 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.