While commonly lumped in with insects, at least in the minds of gardeners, snails and slugs are actually mollusks. Yes, that is the family of clams, oysters and other shellfish. This gives them their main weakness, which is they must remain damp.
During the day they hide, creeping out only at night or on cloudy days. So your not likely to see them, just the damage they do to your plants. Hostas, bird’s nest ferns and other plants of those types are favorite targets. Leaves may be totally eaten. You will find shiny silver trails left by these critters if you look closely at the remaining leaves.
Beer is your best option for control. They love the yeast in the beer. Put out a shallow bowl or a dinner plate and they will climb in, get drunk and not be able to escape. Another option is to put salt around the plants they are eating. Copper is also toxic to critters in this family.