Specifically, I mean from the manual page. The bolded part is the part I can't figure out, can't seem to find any information about it either.
Contains the resulting image from a Snapshot canvas action after On canvas snapshot has run. (Note this expression is not available immediately after the Snapshot canvas action - you can only use it after On canvas snapshot triggers.) The expression returns a data URI of the image file. This can be loaded in to a Sprite or Tiled Background object via Load image from URL, sent to a server or stored locally, or opened with the Browser object in a new tab to save to disk.