It normally comes before the MVP and it is only meant as a practical proof that the core functionality of what you’re trying to build is possible
this also means that PoCs tend to be throw-away pieces of code
You don’t build them to last, you build them to make a point
there might be cases where evolving a successful POC is possible, but there is also the possibility that you’ll find yourself building several POCs in order to proof one point, so planning all of them to be evolved into an actual product might not be the best idea