Final answer:
Gastropods include two common types of slugs: sea slugs and land slugs. Sea slugs live in the ocean and have a shell, while land slugs live on land and do not have a shell.
Step-by-step explanation:
Gastropods include two common types of slugs, which are a type of mollusk. The first type is the sea slug, which lives in the ocean and has a shell. The second type is the land slug, which lives on land and does not have a shell. Both sea slugs and land slugs use their muscular foot to crawl. They belong to the class Gastropoda, which also includes other gastropods like snails and conchs.