Hi,
Does anyone know the name of the panel that appears when you mouse over an icon? And, how does one change its size? For some strange reason mine have become huge relative to the icon size. I do not know what I might have done to change them and I do not know how to restore them to their original size. I have searched the web but cannot find anything that could help. Thanks.

Can you please provide a screenshot of this?

The size of those "previews" is set by the size set for the "Desktop" option in
System Settings->Application Appearance->Icons->Advanced.