Socket.io is a JavaScript library that facilitates real-time, bidirectional communication between clients and servers, making it ideal for applications that require efficient data transfer, such as chat or video conferencing apps. Unlike WebSocket, Socket.io is a custom protocol built on top of other real-time protocols, consisting of both client-side and server-side components that are connected through persistent sockets. The setup involves installing dependencies like Node.js, Express, and Socket.io, and configuring both server and client sides to handle events such as connections, disconnections, and data broadcasting. Socket.io supports event-driven architecture, where events can be emitted and listened to on both ends, facilitating features like joining specific rooms for targeted communication. Debugging is streamlined with the Debug utility, which offers a more refined logging process compared to the previous console-based logging. Additionally, tools like LogRocket can enhance application monitoring by offering session replays and detailed insights into frontend performance, further improving the development process.