The “Pro” products are ones designed specifically for heavy duty work, such as the Death Star Trashcan Mac: https://www.apple.com/mac-pro/
These are computers which have historically had multiple options for graphics cards, higher range choices for CPUs (or on other platforms, multiple CPUs or higher numbers of cores) and generally, easily extended. In a bygone age, these would be referred to as ‘workstations’. This is what you want if your work involves 3D, CAD or high end video work, and there are plenty of good options for Windows (or custom / white box / etc).
Higher end iMacs & MBP are more focused on the “prosumer” type customer that requires better than average performance. They are not well suited to many intensive tasks though — though better at some than others. A pro photographer or someone who is doing some video work can be more than satisfied with this type of product.