A Socket.IO application generally consists of three important components:

1. Socket.IO server: Runs inside your Node.js application and handles client connections and events.
2. Socket.IO client: Runs inside the browser or another application and communicates with the server.
3. Engine.IO: Handles the underlying transport connection and transport upgrades.

The communication workflow is:

1. The browser initializes a Socket.IO client.
2. The client establishes an Engine.IO connection.
3. The connection initially uses an available transport, commonly HTTP long-polling by default.
4. The connection can upgrade to WebSocket when supported.
5. The server accepts the Socket.IO connection.
6. Both sides exchange named events.

The Socket.IO server can also organize connected clients into namespaces and rooms.

A room is a logical grouping of sockets. For example, users belonging to the same project can join a project-specific room and receive project notifications.