Tree snail is a common name that is applied to various kinds of tropical air-breathing land snails, pulmonate gastropod mollusks that have shells, and that live in trees, in other words, are exclusively arboreal in habitat.
Some other species of air-breathing land snails may sometimes be found on tree trunks, or even in the foliage of trees, but this does not mean they live their whole lives in trees, and they are not considered to be tree snails.