An IDL developer utilizes the Interface Definition Language (IDL) to define data types and interfaces in a language-independent manner. They design, code, test and debug programs using IDL, facilitating communication between software components that do not share a language. They work on systems that require data distribution, creating specifications to ensure seamless interaction between different systems. IDL developers also create data models and structures, and may be involved in integrating different software systems. Their role is crucial in developing distributed systems, as they bridge the communication gap between diverse software languages and platforms.