I am not even sure what the difference between squash and pumpkin is - the botanists seem to not recognize it at all, and cooking sources on the Internet are contradictory. I tend to not pay attention and use whatever is available for any recipe which calls for pumpkin (I don't think I've ever tried recipes which specify squash). But recently, I had a talk in chat where derobert suggested that squash may not function in all situation.
When can I continue using squash instead of pumpkin, and when should I expect a difference? And what would the difference be, just a change in taste, or the dish failing completely?