Some gastropods have a extremely elaborate dentacles, or you could call them teeth, that are at the margin of their apertures. Slugs have a remnant shell, or have completely lost their shell, but they can't regain it during their life. So hopeful that clarifies our most basic question about the difference between the two. Now, what about how baby snails and slugs come into the world? Well, a lot of snail and slugs have both male and female reproductive parts, and can create offspring without a partner.