Lead climbing is a roped climbing style in which the climber starts at the bottom of the route with the rope tied to their harness, then clips the rope into protection points (quickdraws on bolted routes, removable gear on trad routes) as they progress upwards. If they fall, the rope catches them at the last clipped piece — often a metre or more below their high point.
This is fundamentally different from top-rope climbing, where the rope is pre-set above the climber and falls are short. In lead climbing, the climber's exposure increases with every clip: a fall just before clipping a high piece could mean falling twice the distance between the climber and the last clipped bolt, plus rope stretch. This makes lead climbing more mentally demanding and the foundation of most performance climbing.
Indoor lead climbing requires a lead-certified belayer and a lead climbing licence at most gyms (typically a short test). The belayer must understand soft catches, rope management, and how to manage slack to keep falls clean. Lead climbing is the standard discipline for sport climbing competitions, outdoor sport routes, and traditional climbing — once you can lead confidently, the entire vertical world opens up.