CORBA or Common Object Request Broker Architecture defines the APIs, communication protocol, and object/service information models to enable heterogeneous applications written in various languages running on various platforms to interoperate. CORBA therefore provides platform and ___location transparency for well-defined objects, which the fundamental underpinnings for a Distributed computing platform.
In a general sense CORBA "wraps" code written in another language into a bundle containing additional information on the capabilities of the code inside, and how to call it. The resulting wrapped objects can then be called from other programs (or CORBA objects) over the network. In this sense CORBA can be considered as a machine-readable documentation format, similar to a header file but with considerably more information.
CORBA uses an Interface Definition Language, or IDL, to specify the interfaces that objects will present to the world. CORBA IDL is only one example of an IDL. In theory the use of an IDL should provide language independance for the code used to implement the object, but in practice the IDL often takes on characteristics of one target language. Such is the case for CORBA, which is used almost exclusively with C++.
CORBA is more than just a language, platform neutral remote procedure call specification. It defines commonly needed services such as transactions and security.