Start10 is for Windows10 only. Used with WindowBlinds, it enables the WindowBlinds skin to be applied to the Start Menu. Without Start10 the Start Menu (and maybe the Start Button?) isn't skinned by WindowBlinds, it remains the normal Windows10.
Start10 can also be used without WindowBlinds to modify the Win10 Start Menu and Start Button.
More details:
https://www.stardock.com/products/start10/