German varies along a dialect continuum which stretches from the North Sea to the south of the Alps. The result is that the language spoken in Munich is not the same as that spoken in Berlin. To complicate matters, the allemannisch dialects spoken in Switzerland are incomprehensible to most other Germanophones, as are the dialects spoken in the north of Italy in Alsace in France and in Belgium, Luxemburg and Liechtenstein. This is where High German or Hochdeutsch comes to the rescue.
High German is standard German
High German is a common dialect everyone can use when wanting to be understood. In Switzerland in particular, people can be described as being bilingual and will revert to High German when their French-speaking compatriotes address them. As such, it is the official language of Germany and Austria and one of the official languages of Switzerland.
High German is the only written German
Rightly do the Germans call dialects Mundarten, ways of the mouth: High German also serves as the written standard. Even in Switzerland, which prides itself on being different from the Germans, no standard spelling of Swiss-German exists and you will be hard-pressed to find anything written in the dialect. Beware if you do! It bears little likeness to High German, either in the mapping of letters and sounds, or in the actual language. The consistency of the written language has allowed the different spoken dialects to evolve their different ways without segregating.
High German is how German should be pronounced
Lastly, High German serves the same purpose in Germany as BBC English does in the UK: in a country with so many regional dialects, it describes the desired way of pronouncing words , particularly in the media where it has very much been enforced. This standard pronunciation comes quite easily, because it is the one which is the most obvious and regular mapping between words and sounds.
In all these contexts, High German denotes a standard, whether in language, writing or speech and not the linguistic family as opposed to the Low German family. This family split off from Low German around 800 ad. and is chiefly noted by its affricate shift: compare pan in English and pfanne in High German. Technically, the language is spoken of as follows:
- Old High German: 800 to 1050
- Middle High German: 1100 to 1350
- Early New High German: 1350 to 1650
- New High German: 1650 to present.
Thankyou wikipedia.com and ethnologue.com among others.