CONCHIGLIONI or SHELLS, so called because they look like mollusk shells, are a very popular short pasta shape.
CONCHIGLIONI is the name for the larger shells and CONCHIGLIETTE for the smallest variety.
Pasta shells are available either smooth or ridged (as in the photo here). It is the perfect shape for holding light sauces. Depending on the size of the shell, they are also served stuffed with any stuffing of your choice before being baked.