The Page Visibility API is a web technology that allows developers to determine the current visibility state of a web page. It helps identify whether a page is in the foreground or background, enabling better resource management and user experience. This API is particularly useful for optimizing performance, such as pausing animations or reducing data usage when a page is not visible. By using the visibilitychange event, developers can listen for changes in the page's visibility state. The API provides properties like document.hidden and document.visibilityState to check if the page is active or inactive. This functionality enhances web applications by allowing them to respond appropriately to user engagement.