A belay is protection for your climber by letting just enough rope out for the rope to catch them if they fall. A belay device creates extra friction in the rope so you can easily hold their fall and transfer the climbers weight to your harness.
Generally these belay devices fall under two categories:
-
Non-assisted e.g.
- Tubular style (reverso, ATC)
-
Assisted braking e.g.
- Petzl GriGri
- Black Diamond Pilot
A Petzl GriGri. It has camming action to assist in braking. You still need to keep your hand on the brake strand.