[2] The key problem with the terms reichsdeutsch, volksdeutsch, deutschstämmig (of German descent, as to citizenship or ethnicity), and related ones is that the usage of the words often depends on context, i.e. who uses them where and when.
The idea of a Kulturnation, as advocated by philosophers like Johann Gottfried Herder (1744–1803) and Johann Gottlieb Fichte (1762–1814), includes German first language, religion (in different forms), and already sometimes German origin, descent or race in a vague sense.
With the 1871 unification of Germany under Prussian leadership, the concept of the German people first acquired a legal-political meaning, which they have retained until now.
German citizenship is passed on from parent to child (jus sanguinis) whatever their ethnicity is.
After World War II and the establishment of the West German Federal Republic of Germany in 1949, the analogous terms Bundesdeutsche (i.e., Federal Germans) and Bundesbürger (i.e., Federal citizens) were colloquially used to distinguish de facto citizens from people entitled to German citizenship, but as a matter of fact unwilling or unable to exercise it, such as citizens of East Germany (DDR-Bürger) and East Berlin, or of the Saar Protectorate.