By filing an international patent appli­cation under the Patent Cooperation Treaty (PCT), the effect of a patent appli­cation can be achieved simultaneous­ly in a large number of PCT states designated in the application. However, a subsequent entry into a national phase of the international application in the respective designated states is required. The patent application is filed centrally and an international search is carried out, which optionally can be followed by an international preliminary examination.

Advantages of an international patent application:
In the PCT states designated in the application, the PCT application has the effect of a national patent application. The PCT application is filed centrally in a single language (e.g. German or English) and the high costs associated with national applications, in particular translation costs and the costs of foreign representatives, are postponed to a later date. If it is not yet clear at the end of the one-year priority period of a first filing in which countries patent protection is required, a PCT application can gain up to 19 additional months.

Here you can find an overview of the PCT states  (external link)