Icon question

If this has been asked and answered I’m sorry I searched quite a good bit but couldn’t find anywhere that had an explanation of icons, or rather something that appears on an icon... recently my wife noted a small cube-type affixed to the bottom of a guests desire and upon interaction the small cube appeared to yield some extra reward as there was a host code displaying the same cube we assumed these were somehow corresponding to each other we just can’t find any info. If anyone could explain or point us to an explanation we’d really appreciate it!

Thanks I’m advance!