Classification of gourds

The Natural Resources Conservation Services offers a classification of plants leading to gourds. It begins with the Kingdom Plantae (plants) and subdivides into Division, Class, Order, and then Family - Cucurbitaceae (cucumber) before getting to the Genus Cucurbita L.  - gourd. The subspecies and Varieties just continue from there.

Soft-Shelled gourds - Colorful and can dry
to a hard skin, but not a thick skin

Miekal and Elizabeth Was explain the gourd varieties as being of two branches: soft shelled and hard shelled gourds. Soft shelled, also called ornamental, gourds are "cucurbita pepo" and having "large yellow edible flowers." These are the colorful gourds found in the grocery store or farmer's markets in the fall and used as decorations for Halloween or Thanksgiving. They can dehydrate to a hard surface and be crafted into decorative or maybe even utilitarian items, but they tend to have a thin shell. Soft shell gourds would be spoon, canteen, and warty gourds.

Hard shelled gourds "lagenaria siceraria" with smaller white flowers tend to have thicker walls when dehydrated and therefore making them better for crafting. Bushel, kettle, and some canteens can have walls requiring power tools to open them for crafting. Bowls, drums, and jars are made from hard shelled gourds. They are generally green or green speckled when newly harvested, but then dehydrate to a brown/tan color covered with dirt and molds which can be washed off before crafting.

 Vickie Henderson Art provides an explanation
about how to clean gourds for crafting.