The term backend development refers to the server-side processing of web applications. It encompasses the database interactions, server-side logic, and application programming interfaces (APIs) that connect the frontend (user interface) to the backend. Backend developers work with languages such as Node.js, Python, Java, and PHP to build and maintain the system's structure. Their focus is on ensuring that the application runs smoothly, processes data efficiently, and communicates effectively with the frontend, ensuring a seamless user experience.