Schnapps is a liqueur derivative and in it's traditional heartland of Bavaria would traditionally be served as two centilitres in a glass called a "Stamperl", a style of shot glass. The glasses are calibrated for this amount, in northern Germany as well as in the south although the type of schnapps differ quite considerably from east to the west.
Should you drink on the North Sea coast, an Enzian, (schnapps made in the Alps) is much more fitting with a hearty snack in the south. Just as a Kirschwasser (cherry schnapps) is served with ham in the Black Forest and in Berlin a Doppelkorn (corn schnapps) with knuckle of pork, sauerkraut and mashed peas.
Just as with food, the preference for high-proof spirits depends on the region. In general schnapps means a clear liquid. But in the northern and eastern part of the country grain is mostly distilled, whereas in the south fruits from the orchards of the Rhine valley and the Lake Constance area are distilled to obtain fruit-flavoured spirits and the berries from the Black Forest are used to create fine, scented spirits.
This also inspires the mind. Oberkirch, the centre of German fruit spirit distilleries, where almost 900 small and tiny distilleries are located, houses a schnapps academy. Graduates from this academy are issued a "Wasserli-Diplom" (Schnapps Diploma).
Schnapps is the generic term for all spirits that warm you up and make you feel good. No matter whether they are clear or coloured, bitter or sweet.