Snail and slug both belong to class Gastropoda of phylum Mollusca. Both are different in terms of their shell. The shell is spirally coiled and made up of one piece protecting the soft body parts in case of a snail. The coils of the shell around the axis are called whorls. The shell is internal in case of a slug. Both also differ in terms of their habitat. Snail leads an amphibious life respiring by means of gill in water and by a pulmonary sac on land. Thus, it is adapted for both aquatic and terrestrial life. Slug is terrestrial and is abundantly found in gardens, cultivated lands and in damp soil.