CORBA stands for Common Object Request Broker Architecture. It is a distributed object architecture developed under the guidance of the Object Management Group (OMG) with the stated purpose of allowing applications to communicate with one another no matter where they are located or who has designed them.
At the heart of the architecture is the ObjectRequestBroker (ORB) which mediates communication betwen objects by providing services to locate, connect and pass data between the objects.
See also:
http://www.inf.fu-berlin.de/~brose/jacorb