Lead climbing (or leading) is a technique in rock climbing where two climbers work together to ascend a climbing route. The 'lead climber' — who is doing the climbing — clips the rope to pieces of protection as they ascend. The 'second' (or 'belayer') stands at the base of the route controlling the other end of the rope, which is called belaying (e.g. if the 'lead climber' falls, the 'second' locks the rope). The term distinguishes between the two roles and the greater effort and increased risk of the role of the 'lead climber'.
Leading a route is in contrast with the alternative climbing technique of top roping, where even though there is still a 'second' belaying the rope, the 'lead climber' faces no risk in the event of a fall and does not need to clip into any protection as the rope is already anchored to the top of the route (e.g. if they fall they will just hang from the static rope). Leading a climbing route is a core activity in rock climbing, and first ascents (FA) and first free ascents (FFA) of new routes must be done via lead climbing.