Postbacks allow you to build interactive web applications. You can wire a Nitrogen element to listen to any Javascript event. When the event fires, the element will post back to the event/1 function on the calling page (or alternatively some delegate module) with the element's tag. This allows you to use the power of Erlang pattern matching to build an event-driven application. Nitrogen postbacks will execute sequentially in the order they are pressed, meaning if one postback is taking a while, clicking another postback will be delayed until the first postback completes.