As the animation above illustrates, the ORB is the communications backbone of CORBA.
One of the significant advantages of the ORB is that clients and servers may concentrate on making CORBA requests and issuing CORBA replies, while the ORB worries about the communications details, such as finding the server and moving data across the network.

An (ORB) object request broker is a piece of middleware software that allows programmers to make program calls from one computer to another via a network.
ORBs promote interoperability of distributed object systems because they enable programmers to build systems by piecing together objects from different ORB vendors so that communication via the ORB can occur.
ORBs handle the transformation of in-process data structures to and from the byte sequence, which is transmitted over the network.
This is called marshalling or serialization. Certain ORBs, such as CORBA-compliant systems, use an Interface Description Language (IDL) to describe the data that is to be transmitted on remote calls. In addition to marshalling data ORBs expose other features, such as distributed transactions, directory services or real-time scheduling.
In OO languages, the ORB takes the form of an object with methods enabling connection to the objects being served. After an object has connected to the ORB, the methods of that object become accessible for remote invocations. The ORB requires definitive means of obtaining the network address of the object that has now become remote.