Deleting all files in a firebase folder?

-->Delete data

The simplest way to delete data is to call remove() on a reference to the location of that data.

You can also delete by specifying null as the value for another write operation such as set() or update(). You can use this technique with update() to delete multiple children in a single API call. <--

the above info was found on this link: https://firebase.google.com/docs/database/web/read-and-write#delete_data

can anybody explain to me what they mean by the last line I think is could help to answer the question in the title. "You can use this technique with update() to delete multiple children in a single API call."

a code spinet would be nice thank you...