If it's something marketed here in the USA for Americans, it is probably fairly sweet and mild mustard, made from coarsely ground seeds.
In Germany, there's really no concept of "German mustard" since they have many types, many of them are regional and some of them quite hot. The most popular kind of mustard in Germany is Mittelscharf (medium hot), a mixture of both yellow and brown mustard seeds.
Weisswurstsenf is a pale mild mustard typically served with the white sausage in its name. Bavarian mustards are darker and sweet. The ones from Duesseldorf tend to be light in colored but hotter.
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In Germany, there's really no concept of "German mustard" since they have many types, many of them are regional and some of them quite hot. The most popular kind of mustard in Germany is Mittelscharf (medium hot), a mixture of both yellow and brown mustard seeds.
Weisswurstsenf is a pale mild mustard typically served with the white sausage in its name. Bavarian mustards are darker and sweet. The ones from Duesseldorf tend to be light in colored but hotter.
More information at this Serious Eats article:
http://www.seriouseats.com/2014/05/mustard-manual-guide-different-types-mustard-varieties-dijon-brown-spicy-yellow-hot-whole-grain.html