Wurstbrot
A Wurstbrot is a slice of bread spread with slices of sausage. Additionally, the bread may be buttered to taste. It is very simple and typical German type of sandwich, generally homemade and popular as a snack, packed lunch as well as for breakfast or supper. The sausage used for spreading is never a bratwurst.
If the sausage is put on a bread roll, it is called Wurstbrötchen and sold at bakeries, the butcher or snack shops. Although a Bratwurst is commonly served with or on a bread roll, too, it is not called Wurstbrötchen.