D-Bus is a message bus, used for sending messages between applications. Conceptually, it fits somewhere in between raw sockets and CORBA in terms of complexity.

This package contains the dbus-launch utility, which automatically launches one D-Bus session bus per X11 display per user. If the dbus-user-session package is also installed, it takes precedence over this package.

See the dbus description for more information about D-Bus in general.