Slugs and snails both belong to the class Mollusca, and are the most recognisable members of the invertebrates. The majority of them are plant-eating, and the main distinguishing feature between slugs and snails, is the possession of a shell on the snail.

Both slugs and snails lay clusters of shiny whitish eggs covered in a water-retaining mucous. The hatching of the eggs may be delayed to the onset of winter, though this is dependent upon the severity of the cold weather, and the species.

Nearly all slugs and snails feed on plant material, and some of the slug species, in particular, are significant pests of agriculture and horticulture.