Earlier quoted context omitted.
Does anyone have a breakdown of how .NET Core/4.5/MVC/etc interact, are different, etc?
.Net Core: cross-platform build tooling, minimal API .Net Standard: cross-platform comprehensive API .Net 4.5: Windows-only build tooling + comprehensive API .Net MVC: Windows-only web framework built on .Net 4+
Mono is another implementation of the standard.. cross-platform too, but this time compatible with the actual .NET Framework, i.e. 4.5.