What is the difference between a sugar pumpkin and a regular pumpkin (like you make into a jack-0-lantern)?

I've been researching recipes online for fresh pumpkin and all of the recipes I've found call for a medium sugar pumpkin. Is a regular, garden variety, Halloween-type pumpkin interchangeable in recipes with a sugar pumpkin? I have two of them (not cut into jack-0-lanterns) and would like to cook them.
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