I'm sure you already know about the Qt Project File since we have mentioned it countless times throughout the book. A .pro file is actually the project file used by qmake to build your application, library, or plugin. It contains all the information, such as links to the headers and source files, libraries required by the project, custom-build processes for different platforms/environments, and so on. A simple project file could look something like this:
QT += core gui widgets TARGET = MyApp TEMPLATE = app SOURCES += main.cpp mainwindow.cpp HEADERS += mainwindow.h FORMS += mainwindow.ui RESOURCES += resource.qrc
It simply tells qmake which Qt modules should be included in the project, what the name of the executable ...