The Patent Cooperation Treaty (PCT) patent application is a temporary patent application which preserves your right to file a foreign national patent application in countries which participate in the treaty for an additional 18 months before filing a national application if the PCT application is filed within 12 months of your earliest US patent application filing (either provisional or non-provisional). That means you would not have to file a national application outside the U.S. for a total of 30 months from your initial filing (priority date). The vast majority of countries that have a patent system participate in the PCT system (Taiwan the most notable exception). The PCT can even be used to delay the filing of a regular US patent application off of a provisional application, if filed properly. While a PCT patent application does not issue as a patent, the application is examined and a search report is provided which includes a general opinion as to patentability from a patent examiner. While not obligated, many patent examiners in the U.S. and other countries follow the results of the PCT opinion since it saves them the trouble of doing the work themselves. The requirements for a PCT patent application are similar to a regular US application and in most cases your U.S. patent application can be filed as a PCT application.