They live within the soil. They come back to the surface in rainy weathers, because their lives are in danger when their homes fill with water. After the rain stops and their holes are dried, they go back under the ground. They make the soil which they live in useful for the plants. So, the plants in the soil with worms grow better. They live 2 - 6 years in average.
In this story, you will be surprised at how much a little worm can teach his snail friend.