It allows WordPress to send and receive real-time data, such as autosave revisions, plugin notifications, and session management. The API essentially helps in keeping your browser session up to date with the server, allowing you to experience certain real-time functionalities.
The Heartbeat API works by making periodic requests from your browser to the server. By default, it sends a POST request to the
admin-ajax.php file every 15 seconds on the admin dashboard and every minute on post edit pages.
This can create unnecessary server requests, leading to increased server load and potential conflicts with other plugins or themes.