Flywheel has teeth on it for the starter to engage.
Flexplate is just a plate that connects crankshaft to torque convertor, like old 6 cyl C-4 set ups or Mopars that have the starter engaging teeth on the convertor.
Ok that makes sense. I thought flex plates were for autos but I saw some one selling a auto with what they called a fly wheel. It thru me off. Thanks guys.