Molluscs are soft-bodied animals that are classified based on the number of shells they possess. They have three main body parts - a head containing sense organs, a foot used for movement, and a visceral mass containing most of the internal organs. Within the visceral mass is the mantle, which secretes and maintains the exoskeleton in the form of shells. Exceptions include snails, which are hermaphrodites capable of functioning as both male and female.