Upwind in heavy gusts and when a boat is getting overpowered it might suddenly heel over and turn the bow windward, "shooting the sun". Cruising sailors usually will slack the main sheet to regain control. Racers or keen cruisers don't do this because it would considerably increase the drag of the rig and worsen the situation. Also, they like to keep the boat running. The ultimate maneuver getting control then is to "throw off" the vang. This opens abruptly the main sail leech allowing for better wind flow. Although just a small extension of the boom would perform the same twist of the sail, the skipper needs his hand to hold tight and do the steering.
This is what the Panic Release is for. One push will extend the vang for an adjustable length of time, another push will stop it and the next will redo it. Turning the button restores the normal function and turns off the indicating light.
These functions can be used also for other maneuvers as tacking, or quickly changing from upwind to downwind trim.