It's part of the senses, not a stinger. Snakes have no eyelids, but they can see well at short distances. They have no ear holes, but they can feel vibrations in the ground. Snakes swallow their food whole. Their jaws are made of separate sections joined only by stretchy ligaments, so they can open wide to swallow large food animals.
Snakes eat a number of garden pests, such as slugs.
When a snake is growing, it sheds its skin as often as every 4 or 5 weeks. The shed skin looks like thin clear plastic, with every detail of the scales still visible, even the eyeball cover.