Cure

Fresh sausage that will be cooked at a high temp, above 200*, and fully cooked to over 160* does not need a cure. Breakfast sausage, Italian sausage, fresh bratwurst are examples of this.
Sausage that will be smoked at lower temps for many hours need a cure. Kielbasa, Polish sausage, smoked sausage are examples of this.

Probably the easiest way to decide if it needs cure is whether you will smoke it or if it will be fermented.  Smoked sausages like  Kielbasa, Kabanosy, Frankfurters, hot dogs will use cure #1.  Fermented sausages like summer sausage, peperoni or salami will use cure #2.  Fresh sausages like breakfast sausage, most bratwursts, Italian sausage do not require cure.  These are usually cooked or frozen within a few days of stuffing. 

These are just generalizations and there are exception to these, but best not worry about those until you get some more experience.