From Forum Nokia Wiki

D-Bus is an inter-process communication (IPC) system, which make possible for applications to talk to one another. It is based on a message bus mechanism. Many Maemo applications and frameworks use D-Bus as communication engine. Examples include the GUI framework Hildon and the Internet Communication Framework Telepathy.

D-Bus has higher-level bindings specific to particular frameworks such as Qt, GLib, Java, C# and Python.

External Links:

D-Bus Project