A Websocket provides a unique way of monitoring the incoming email of a particular address. With a single persistent connection all content from an email address can be forward over the Websocket. This allows your application to be notified of an incoming emails as soon as it arrives. This helps reduce the number of API calls and reduces latency from when the email arrives and your application responds to it.
Want to see it in action? The WebSocket Test Page allows you to show how it works with no programming involved.