In Germany, there are certain regulations for professions. These regulate, for example, the tasks, responsibilities and expertise associated with certain professions.
In many cases, you will need to have this officially confirmed. This process is called "recognition".
For people who do not come from the European Union (EU), the European Economic Area (EEA) or Switzerland, recognition is also required for a visa in many cases.
Recognition is not free of charge. The procedure itself and the preparation incur costs.