What can I do with it? Can I save what I draw on it?

It's not a finished feature. It was unintentionally left in during an update.

It's intended to be a site drawing page, where people can draw on a public board and it'll show everyones drawings. Right now, it's just a temporary board no one else can see you draw in. Guess it's fine to doodle on.

I see. Good luck finishing it.

Maybe after a period of time the board auto-saves and users can download the saved version.