The official language of Austria is German, which in its standard national variety known as Austrian (High) German is generally identical to the German used in Germany, with some important differences in vocabulary (many of which refer to the language of the kitchen or the home) and a fairly distinct accent. Most Austrian words are borrowed from Austro-Bavarian, but the languages of neighboring countries have also had an influence. Other languages have some official status in various localities (e.g. Slovene in Carinthia, Burgenland Croatian, and Hungarian in Burgenland).
However, the first language of almost all Austrians is not German, but local dialects of Austro-Bavarian (Boarisch) (also spoken as a first language by many people in Bavaria and South Tyrol, Italy), with the exception of Vorarlberg, where it is replaced by Alemannic (also the first language of the inhabitants of German-speaking Switzerland and Liechtenstein, further of Baden-Württemberg, especially in the southern regions, and partly of Alsace, in France). These two languages belong to the Upper German language family but are only partially intelligible with each other and with German. Especially in big cities, almost everyone will also be able to communicate in German, even if only in conversation with foreigners (including northern Germans). Most Austrians can understand the dialect of another region, but in Vorarlberg, they have the greatest difficulties because it is a German-speaking region.
English is widely spoken and menu translation is the one area where most tourists have language problems. Even competent people who speak German or Austro-Bavarian may find that they are answered in English, and it is not unusual to hear Austrians speaking in English! However, in rural areas, older people sometimes do not speak English. It can therefore be useful to learn some basic phrases in German or Austro-Bavarian when you visit these places.
In the regions of Austria bordering Italy, such as Tyrol, Italian is widely spoken, although the majority language on the Italian side (except in the provincial capital of Bolzano) is still German (in practice Austro-Bavarian).
Due to the immigration to Austria after the Second World War, you will certainly meet people in the big cities whose mother tongue is Bosnian/Croatian/Serbian and Turkish.
In general, when speaking German, Austrians tend to pronounce the vowels longer and use a pronunciation that is regional but authentic, elegant and melodic; some even consider it the beautiful form of German. Moreover, the “ch”, “h” and “r” are not pronounced as harshly as in Germany, making the accent much softer.