When a form is opened, SQL generates an XML file that represents the definition and structure of that form. It is a snapshot of what the form looks like and how it behaves. An XML file is then saved in the backend cache so that the next time the form is needed, the system can populate it without having to rebuild it from scratch. This is done for performance reasons, as retrieving a cached version is faster than regenerating the form definition repeatedly.
To Purge the Cache, select the icon from the form header. Afterwards, you will need to refresh the browser for these effects to take place. One the cache has been purged; a green toast will appear at the bottom of the screen.