What "belay" means in rock climbing

Belay is a safety technique used in rock climbing to protect the climber from falling. The process involves a climbing rope being fed through a device and attached to the belayer's harness. When top rope climbing, the belayer stands at the bottom of the climb and maintains tension on the rope to keep the climber safe. When lead climbing, the belayer lets out more rope (called slack) as the climber ascends.