GObject is the part of the GLib library that provides an object and type system for C programs. Although C as a language does not provide objects or classes, GObject makes it possible to write object-oriented C programs.

GObject provides a fundamental GType, the base for the whole type system, from which types such as ints and strings are derived. Then, there is GObject itself, the base class for all other classes. Objects can emit signals to notify the caller when something interesting happens. For example, a Button object could emit a clicked signal to indicate that it has been pressed and released.

GObject is introspectable, which means that you can ask the GObject system for the class types that are defined, the methods they support, their signals, etc. GNOME's language bindings are built on top of this introspection information. Instead of writing wrappers by hand to let GNOME APIs be called from other programming languages, language bindings use the introspection information from GObject to auto-generate those wrappers themselves.

You normally don't need to be concerned with GObject itself if you are programming for GNOME with an object-oriented language. However, making yourself familiar with GObject's concepts, such as signals and slots, will make your life easier as a GNOME programmer.