"Server-side" refers to operations that are performed on a web server rather than on a user's device. When a user requests information from a website, the server processes that request, retrieves the necessary data, and sends it back to the user's browser. This approach allows for more complex computations and data management, as the server typically has more resources than individual devices. Common technologies used for server-side development include PHP, Node.js, and Python. These languages enable developers to create dynamic web applications that can interact with databases and handle user requests efficiently. Server-side processing is essential for maintaining security and managing user sessions effectively.