pbxproj file extension
The pbxproj file format is generated by Xcode .
prbxproj files are data files which contain information such as the list of source code and resource files, together with the build properties.
Group data which is also saved in a pbxproj file is used to organize resource files in a hierarchy of virtual folders.
The pbxproj files is stored within the .XCODEPROJ file for the project, even though the Xcode interface displays the project.pbxproj file for the project.