Basics

The Qt framework has a number of extensions at are implemented on top of standard C++ to support a generalized intra-objects communications mechanism for events. In Qt this is called "Signals and Slots". A signal is an event that an object will emit under some set of conditions. A slot is a method of an object that will receive an event (signal). The connect method is used by event consumers to connect their slots to other objects emitted signals.

Reference: Qt Signals and Slots