Qt Core is one of the modules supported by Qt. This module has loads of useful classes, such as QObject, QCoreApplication, QDebug, and so on. Almost every Qt application will require this module, hence they are linked implicitly by the Qt Framework. Every Qt class inherits from QObject, and the QObject class offers event handling support to Qt applications. QObject is the critical piece that supports the event handling mechanism; interestingly, even console-based applications can support event handling in Qt.