There are 2 ways, it depends on the type of snake. They can unhinge their jaw, swallow the thing whole. They can't digest fur feathers or claws so they regurgitate that after the rest is digested. The other way is with their venom, the victim is bit and injected with the powerful venom, this will start to break down the tissues inside of it. Then the snake is able to suck up the liquid remains and enough a meal.