Server-Sent Events (SSE) is a server-push technology enabling a web server to send automatic updates to a client's browser over a single HTTP connection. Unlike WebSockets which facilitate two-way communication, SSE establishes a one-way channel from server to client, making it ideal for scenarios where the server needs to stream real-time data without requiring client responses.

Key characteristics of SSE include:

• Simple implementation using standard HTTP protocol
• Automatic reconnection when connections drop
• Native browser support through the EventSource API
• Efficient, text-based data streaming (typically using UTF-8)

Common applications include:

• Live sports scores and stock tickers
• Real-time news feeds and social media updates
• Notification systems and dashboard updates
• Progress indicators for long-running server processes

To implement SSE, the server sets the Content-Type: text/event-stream header and sends data in a specific format with "data:" fields. The client then uses JavaScript's EventSource interface to listen for incoming messages. Compared to alternatives like polling or WebSockets, SSE offers lower latency than periodic polling and simpler implementation than full-duplex WebSocket connections when only server-to-client communication is needed.

SSE provides an efficient solution for real-time web applications where the primary requirement is server-initiated updates without the complexity of bidirectional communication protocols.