Interface Description Languages describe an interface in a language-independent way, enabling communication between software components that do not share one language.
Interface Description Languages are commonly used in Remote Procedure Call software. In these cases the machines at either end of the link may be using different operating systems and computer languages. IDLs offer a bridge between the two different systems.
Software systems based on IDLs include Sun's ONC RPC, The Open Group's Distributed Computing Environment, IBM's System Object Model, the Object Management Group's CORBA (which implements OMG IDL, an IDL based on DCE/RPC), Mozilla's XPCOM, Facebook's Thrift and WSDL for Web Services.