Traditional climbing — almost universally shortened to "trad" — is a roped climbing discipline where the lead climber carries a rack of removable protection (cams, nuts, hexes, slings) and places these pieces into cracks and features in the rock to clip the rope to. When the second climber follows the route, they remove every piece. The rock itself is left untouched — no permanent bolts, no scars, no hardware visible from below.
This is the original form of free roped climbing and remains the dominant style at most British, US Western, and many continental European crags. Trad climbing demands more skill than sport climbing because the climber must judge rock quality, choose appropriate gear sizes, place them correctly under stress, and accept that protection is only as good as their own judgment. Falls in trad can be longer and more consequential than in sport climbing if a piece pulls.
Trad climbers carry a "rack" — a colour-coded selection of cams (spring-loaded camming devices that lock in parallel cracks), nuts (passive metal wedges for tapered cracks), and slings. Routes are graded with both a difficulty grade and an "R" or "X" suffix to indicate whether protection is sparse or runout. Most climbers learn trad after a year or more of sport experience, ideally with a mentor or guided course.