First off: What's the difference between pumpkins, gourds, and squash?
This is not as dumb of a question as it might seem. All three are subcategories of the Cucurbitaceae family, meaning they are all fruits that stem (hehe) from herbaceous vining plants. Their genetics and terminology tend to overlap to a bewildering degree.
The word "pumpkin" doesn't really pertain to much, botanically, as it is really just a type of squash (as is butternut squash or acorn squash, for example). While the word "gourd" is meant to represent a different branch of the Cucurbitaceae family.
Generally, gourds are going to have rigid exteriors, and don't have an abundance of "fleshy" insides that make them good eats -- unlike squash. Most squash is cultivated for consumption, while most gourds are grown for purely decorative purposes. So really, when people define something as a gourd, they basically mean "inedible squash."
But again, these definitions are more circumstantial than anything else. A full-grown pumpkin can be considered a squash -- but when you think about the miniature pumpkins (the ones you might paint in kindergarten), those are more like gourds, because they are small, extremely hard to open, and don't contain much edible substance.