Correct--mealworms are the larvae of a darkling beetle.  Superworms are bigger, and still larvae but I don't remember the beetle.  But neither are composting types (though if you farm them, the grass is good for compost bin).
Many chicken owners do farm them to use as a protein supplement.  They are easy, but done indoors as cool temps don't allow for fast maturity.  There are whole long threads on it. If you're looking for garden or composting worms, you want red wiggler type.