Where are the differences between snails and slugs?

Have you ever wondered how are snails and slugs different? Are slugs just snails without a "house"?

Pretty much. Snails and slugs are closely related and they are both part of the same class of creatures called gastropods ("Gastropods" means "stomach walker"). The main difference between a snail and a slug is that a snail has an external shall. When snails feel danger, they will quickly sneak back inside their shells, while slugs would have to find a small place to squeeze into. In addition, slugs may produce more mucus across their body because slugs have a higher surface area of exposed flesh

See what a semi-slug is.