THE SWISS GERMAN LANGUAGE
First, keep in mind that Switzerland gets four official languages: French, Italian, German and Romansh. In fact, the Swiss German language refers to the Alemannic dialects of the country. Also, it is very close to Alsatian and to the dialects of South West Germany. As well as to Austrian Vorarlberg and dialects found in the Italian Alps.
In contrast to most dialects in Europe, people of both low or high status still speak Swiss German. This, both in countryside and cities, and in all contexts of the daily life. Indeed, using a dialect there does not refer to social status. Thus, there is no feeling of social difference in using it.
Written or oral
Standard German focuses mainly to written words, whether formal (newspapers, books) or informal (private use). This is why people often call it "written German". Most younger people now use it with SMS, emails, postcards, etc. But there is no standard spelling rules. Also, the written language accepts a lot of dialect words, as Helvetisms.
Such a situation is called "codic" or "medial" diglossia, as dialect is the spoken language, and standard German the written language. We can observe the same thing in the Arab countries. There, people use the national dialect, but use literal Arabic in writing.
When spoken, German limits to certain formal cases. For instance: in speeches, at school or in parliaments. But also in the main radio and television news programmes or in the presence of foreigners who speak Standard German.
In fact, the Alamans, a group of German tribes, brought their language from the 400s. Over the time, it slowly evolved into Swiss German.
NOT EASY AT ALL
Depending on your origin
First, many people consider most Swiss German dialects quite hard to understand. This is the case whether you are a German speaking from Germany or Austria. Same thing to people who grew up in the French or Italian part of the country and then learned standard German.
Then, a German speaking Swiss with French knowledge can adapt to an informal conversation between French speakers. But the reverse does not work. In fact, with a French speaking person, German speaking Swiss will speak either German, French or English.
Finally, Italian speakers know more about Alemannic dialects. On the one hand, the latter are strong in the Swiss border region of Ticino. On the other hand, cross border commuters often study in the German speaking part of the country.
For a long time now, all regions have been making great efforts to overcome the issues. For instance, tv and radio provide news in German. Also, many German speaking members of government appear on French language programmes. Finally, those who dream of a national career try to understand and speak enough one dialect or another.
To that, the fact to move to a region or another has allowed to weaken differences between dialects.
Since schools teach German in the German speaking part, they often transcribe Swiss German using the German script. But there are no spelling rules. So, everyone transcribes their own dialect in their own way.
The oral Swiss German follows grammar rules which vary from dialect to dialect with no rule. There are descriptive grammars as well as dictionaries. This is the case at least for the main variants of Zurich, Bernese, Basle and Lucerne. Compared to Standard German, the syntax of Swiss German is much simpler, and the word order, strict.
The Swiss German language has four tenses: future, present, past compound and past super compound. However, in speech, people rarely use the furture tense coming from standard German. Instead, we combine the present tense with the particle dä(nn), or use a form like the French "je vais faire"/ich gang ga mache. Then, the super compound past tense is similar to the French "plus que parfait". Finally, we always replace the German preterit tense by the past compound tense in the Swiss German language.
Also, people often use the subjunctive and conditional tenses. By the way, these forms often respect the German's ones.