The back-end refers to the part of a web or mobile application that handles server-side logic, operations, and databases, which are essential for the application’s functioning. This part includes servers, databases, and server-side applications that process user requests, perform calculations, manage data storage and retrieval, and ensure data security and integrity. Technologies commonly used for back-end development include programming languages like Java, Python, Ruby, PHP, and frameworks like Node.js, Django, and Spring.

Back-end developers focus on building and maintaining the infrastructure that supports the front-end. This includes creating and managing APIs, integrating with third-party systems, and optimizing server performance. A crucial aspect of the back-end is database management, using systems like MySQL, PostgreSQL, MongoDB, and others. Back-end developers work closely with front-end developers to ensure that data is correctly transmitted and displayed to the end-user, ensuring that the application is robust, scalable, and secure.