Complex sentence: The term "ramshorn snail" is used in the aquarium trade to describe various kinds of freshwater snails whose shells are planispiral, meaning that the shell is a flat coil.
Split into simpler sentences: The term "ramshorn snail" is used in two different ways. In the aquarium trade it is used to describe various kinds of freshwater snails whose shells are planispiral, meaning that the shell is a flat coil.