Server-Sent Events, also known as EventSource, is a technology that allows a web server to send data to a client in real time. This technology is used to create interactive and dynamic web applications, such as chat rooms, live feeds, and real-time notifications.

Server-Sent Events work by establishing a persistent connection between the client and the server. The client sends a request to the server to open a connection, and the server responds by sending an event stream to the client. This event stream can then be used to transmit data from the server to the client in real time.

One of the main advantages of Server-Sent Events is that it allows for a one-way communication between the server and the client. This means that the server can send data to the client without the client having to send a request. This is especially useful for applications that need to update the client with new information on a regular basis.

Another advantage of Server-Sent Events is that it is very efficient. The event stream is a lightweight and simple protocol that allows for fast and reliable transmission of data. This makes it ideal for applications that require high levels of traffic or need to send large amounts of data in real-time.

Server-Sent Events also support cross-origin resource sharing (CORS). This means that the server can send events to clients from different domains, making it easier to create cross-domain applications.

Overall, Server-Sent Events is a useful technology that allows for real-time communication between a web server and a client. It is efficient, easy to use, and has the ability to support cross-domain applications. If you are looking to create a dynamic and interactive web application, Server-Sent Events is definitely worth considering.