An application that enables a user to post or advertise his availability status. Presence technology is a feature of instant messaging (IM) systems and some IPBX systems.Through presence technology a user can indicate his availability as online and available for e-mail or IM but unavailable for telephone calls, unavailable for IM or telephone calls, out to lunch, out of the office on business or vacation but returning on a certain date, and so on. See also IM and IPBX.