The green snubber will allow your ball to bounce along the bottom without ripping the boom off your downrigger. Or, even worse, rip your 'rigger from your boat. Also, if you have a Scotty electric, the snubber will keep the 'rigger from bouncing back up at you in the boat (safety measure).

The hair trigger release has a male part and a female part. The female part has the hole (obviously) and you run your mainline in the groove of the male end (teathered to the female part) before you stick it in to the female part. You can adjust the tension using the dial provided on the female part. When a fish takes your lure the force on the line will pull the male end out of the female part.

Does that make sense?