There is no difference.
Industrial Design is an old term that evolved out of Tool Design from the Industrial Revolution. Some of the very old ID programs were actually originally called Tool Design, craftsmen who drew and built prototype patterns that steel tools were cut from.
As Tool Design morphed to Industrial Design to better describe the education designers received in manufacturing processes and designing for mass production, Industrial Design is currently morphing to Product Design to better explain our knowledge of the entire product experience from research, to line building, to interaction design, to user experience.
Industrial Design, based in Industrial Revolution era thinking, implies a tie explicityly to manufacturing. Product Design makes us responsible for the entire process and is a more encompassing term.