Product realization starts with a verified product design. A verified design is one which meets all performance specifications, while exhibiting the other features that make it complete, in a commercial sense.
Realization starts when that design is released for tooling, and any equipment is ordered for production. As the tools and processes are completed, the design moves through a variety of additional verification stages, typified by changes in the processes used to create a prototype. A protoytpe made from production tooling is a different animal from a prototype made from prototype tooling, even if it is assembled on a production automation line.
Once the tooling and automation are able to produce parts, those parts are then verified again to establish the process capability of the tooling, verify that the product still meets specification, and to establish that the assembly equipment is capable. At the end, the supply chain is complete with a component set released for production, and an assembly line, fully ready to produce.