Dual citizenship is a term used to describe a person who has citizenship in two countries. This means that they probably were born in one country and then moved and has lived and worked in another country for a longer period of time. In this case, the person would have to apply for the citizenship in the new county. In Austria, it is not so simple.
Austria does allow dual citizenship, but it is with limited means. This mean that the person in Austria had to get their dual citizenship at the time of their birth. For example, an Austrian may have been born from Austrian parents, but the baby was born in the United States. That way, they would have dual citizenship with Austria and the United States.