Snails carry coiled shells on their backs. Slugs don't. Most slugs and snails live in water. Land snails and slugs like rain and wet and produce mucous to travel across land. Snails and slugs bury themselves in the ground or under things during dry weather.
Snails and slugs use the long tentacles on their heads to feel around and the smaller stalked eyes to see.
The snail's shell grows with it. As the snail grows, the opening rim of its shell grows in larger and larger rings.